combine: stop eagerly evaluating consts

`super_relate_consts` eagerly evaluates constants which doesn't seem too great.

I now also finally understand why all of the unused substs test passed. The reason being
that we just evaluated the constants in `super_relate_consts` 😆

While this change isn't strictly necessary as evaluating consts here doesn't hurt, it still feels a lot cleaner to do it this way

r? `@oli-obk` `@nikomatsakis`

combine: stop eagerly evaluating consts

`super_relate_consts` eagerly evaluates constants which doesn't seem too great.

I now also finally understand why all of the unused substs test passed. The reason being
that we just evaluated the constants in `super_relate_consts` 😆

While this change isn't strictly necessary as evaluating consts here doesn't hurt, it still feels a lot cleaner to do it this way

r? `@oli-obk` `@nikomatsakis`

Rollup of 8 pull requests

Successful merges:

 - rust-lang#81351 (combine: stop eagerly evaluating consts)
 - rust-lang#82525 (make unaligned_references future-incompat lint warn-by-default)
 - rust-lang#82626 (update array missing `IntoIterator` msg)
 - rust-lang#82917 (Add function core::iter::zip)
 - rust-lang#82993 (rustdoc: Use diagnostics for error when including sources)
 - rust-lang#83522 (Improve fs error open_from unix)
 - rust-lang#83548 (Always preserve `None`-delimited groups in a captured `TokenStream`)
 - rust-lang#83555 (Add #[inline] to io::Error methods)

Failed merges:

 - rust-lang#83130 (escape_ascii take 2)

r? `@ghost`
`@rustbot` modify labels: rollup