Implement (de)serialization for Box, Arc, and Rc, and serialization for references

[progval]

We can't implement deserialization for references because something has to own them.

Unfortunately, we can't have a blanket impl for Deref:

error[E0119]: conflicting implementations of trait `traits::copy_type::CopyType` for type `[_; _]`
  --> epserde/src/impls/deref.rs:19:1
   |
19 | impl<T: Deref<Target: CopyType>> CopyType for T {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[_; _]`
   |
  ::: epserde/src/impls/array.rs:19:1
   |
19 | impl<T: CopyType, const N: usize> CopyType for [T; N] {
   | ----------------------------------------------------- first implementation here
   |
   = note: upstream crates may add a new impl of trait `std::ops::Deref` for type `[_; _]` in future versions

and also not for Borrow<_>:

error[E0119]: conflicting implementations of trait `traits::copy_type::CopyType` for type `[_; _]`
  --> epserde/src/impls/deref.rs:19:1
   |
19 | impl<Borrowed: CopyType, T: Borrow<Borrowed>> CopyType for T {
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `[_; _]`
   |
  ::: epserde/src/impls/array.rs:19:1
   |
19 | impl<T: CopyType, const N: usize> CopyType for [T; N] {
   | ----------------------------------------------------- first implementation here

error[E0207]: the type parameter `Borrowed` is not constrained by the impl trait, self type, or predicates
  --> epserde/src/impls/deref.rs:19:6
   |
19 | impl<Borrowed: CopyType, T: Borrow<Borrowed>> CopyType for T {
   |      ^^^^^^^^ unconstrained type parameter

[progval]

This doesn't work as well as I'd like. For example, this code:

use std::borrow::Borrow;
use std::marker::PhantomData;

use epserde::prelude::*;
use epserde::Epserde;

#[derive(Epserde)]
pub struct InnerStruct<T: AsRef<[u64]>> {
    data: T,
}

#[derive(Epserde)]
pub struct OuterStruct<T: AsRef<[u64]>, BorrowInner: Borrow<InnerStruct<T>>> {
    inner: BorrowInner,
    marker: PhantomData<T>,
}

fn main() {
    let original = OuterStruct {
        inner: InnerStruct {
            data: vec![1, 2, 3],
        },
        marker: PhantomData,
    };

    let mut file = std::io::Cursor::new(vec![]);
    original.serialize(&mut file).expect("Could not serialize");
    let data = file.into_inner();
    let deserialized = <OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>>::deserialize_eps(&data)
        .expect("Could not deserialize");
}

Should make it possible to serialize OuterStruct<Vec<u64>, &InnerStruct<Vec<u64>>>. But when I try to use it (even with the regular OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>), I get this:

   Compiling epserde v0.8.0 (/home/dev/epserde-rs/epserde)
error[E0599]: the function or associated item `deserialize_eps` exists for struct `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>`, but its trait bounds were not satisfied
   --> epserde/examples/borrow.rs:29:72
    |
13  | pub struct OuterStruct<T: AsRef<[u64]>, BorrowInner: Borrow<InnerStruct<T>>> {
    | ---------------------------------------------------------------------------- function or associated item `deserialize_eps` not found for this struct because it doesn't satisfy `_: DeserializeInner` or `_: Deserialize`
...
29  |     let deserialized = <OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>>::deserialize_eps(&data)
    |                                                                        ^^^^^^^^^^^^^^^ function or associated item cannot be called on `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>` due to unsatisfied trait bounds
    |
    = note: the following trait bounds were not satisfied:
            `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
note: the trait `epserde::deser::DeserializeInner` must be implemented
   --> /home/dev/epserde-rs/epserde/src/deser/mod.rs:264:1
    |
264 | pub trait DeserializeInner: Sized {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `deserialize_eps`, perhaps you need to implement it:
            candidate #1: `epserde::deser::Deserialize`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `epserde` (example "borrow") due to 1 previous error

It's an improvement over what we got before this PR though:

   Compiling epserde v0.8.0 (/home/dev/epserde-rs/epserde)
error[E0599]: the function or associated item `deserialize_eps` exists for struct `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>`, but its trait bounds were not satisfied
   --> epserde/examples/borrow.rs:29:72
    |
13  | pub struct OuterStruct<T: AsRef<[u64]>, BorrowInner: Borrow<InnerStruct<T>>> {
    | ---------------------------------------------------------------------------- function or associated item `deserialize_eps` not found for this struct because it doesn't satisfy `_: DeserializeInner` or `_: Deserialize`
...
29  |     let deserialized = <OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>>::deserialize_eps(&data)
    |                                                                        ^^^^^^^^^^^^^^^ function or associated item cannot be called on `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>` due to unsatisfied trait bounds
    |
    = note: the following trait bounds were not satisfied:
            `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: TypeHash`
            which is required by `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: AlignHash`
            which is required by `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `&OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: TypeHash`
            which is required by `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: AlignHash`
            which is required by `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
            `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::DeserializeInner`
            which is required by `&mut OuterStruct<Vec<u64>, InnerStruct<Vec<u64>>>: epserde::deser::Deserialize`
note: the trait `epserde::deser::DeserializeInner` must be implemented
   --> /home/dev/epserde-rs/epserde/src/deser/mod.rs:264:1
    |
264 | pub trait DeserializeInner: Sized {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    = help: items from traits can only be used if the trait is implemented and in scope
    = note: the following trait defines an item `deserialize_eps`, perhaps you need to implement it:
            candidate #1: `epserde::deser::Deserialize`

For more information about this error, try `rustc --explain E0599`.
error: could not compile `epserde` (example "borrow") due to 1 previous error

but still not enough.