Remove the Build traits from bit_vectors and int_vectors

[kampersanda]

Summary

• Remove bit_vectors::Build and int_vectors::Build, along with their impls and prelude re-exports.
• Change WaveletMatrix::new to take a closure that builds each layer from a BitVector.
• Update module docs, tests, and the bench crate accordingly.

Why

The Build traits were an over-abstraction:

• bit_vectors::Build::build_from_bits(bits, with_rank, with_select1, with_select0) took three positional bools whose meaning differed per type. BitVector ignored all of them, Rank9Sel ignored with_rank, DArray ignored with_select1, and SArray returned an error for with_select0. Unsupported features were only detected at runtime.
• Every impl just forwarded to the type's own constructors (from_bits, enable_rank, select1_hints, ...).
• int_vectors::Build had no generic users at all, wrapped infallible constructors in Result, and hid DacsOpt's max_levels parameter.
• The only generic user was WaveletMatrix::new.

New WaveletMatrix API

pub fn new<F>(seq: CompactVector, build_layer: F) -> Result<Self>
where
    F: FnMut(BitVector) -> B,

let wm = WaveletMatrix::new(seq, Rank9Sel::new)?;
let wm = WaveletMatrix::new(seq, |bv| Rank9Sel::new(bv).select1_hints().select0_hints())?;

The bench crate keeps the previous configurations (Rank9Sel with both select hints; DArray with enable_rank().enable_select0()).

Notes for reviewers

• Breaking change: public traits are removed and WaveletMatrix::new gains an argument. This should go into 0.10.0.
• SArray still cannot be used as a WaveletMatrix layer because it lacks select0. Previously this failed at construction with an error; now it panics when select is called. The new docs state that layers must support both select1 and select0.
• SArray's test_rs_build_with_s0 was removed since the code path it tested no longer exists.

Test plan

• cargo fmt --all --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings -W clippy::nursery
• cargo clippy --all-targets --no-default-features -- -D warnings -W clippy::nursery
• cargo test / cargo test --release --no-default-features
• cargo doc --no-deps

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