rewrite `optimize` attribute to use new attribute parsing infrastructure
r? ```@oli-obk```
I'm afraid we'll get quite a few of these PRs in the future. If we get a lot of trivial changes I'll start merging multiple into one PR. They should be easy to review :)
Waiting on #138165 first
Port `#[rustc_as_ptr]` to the new attribute system
It might make sense to introduce some new parser analogous to `Single`, but even more simple: for parsing attributes that take no arguments and may appear only once (such as `#[rustc_as_ptr]` or `#[rustc_const_stable_indirect]`). Not sure if this should be a single `impl` parsing all such attributes, or one impl per attribute. Or how it will play along with the upcoming rework of attribute validation. Or how these argumentless attributes should be called (I've loosely referred to them as `markers` in the name of the new module in this PR, but not sure how good it is).
This is a part of rust-lang/rust#131229, so
r? `@jdonszelmann`
---
For reference, the `#[rustc_as_ptr]` attribute was created back in rust-lang/rust#132732 as a followup to rust-lang/rust#128985.
- Remove dead link to `rustc_attr` crate.
- Add link to `rustc_attr_parsing` crate.
- Split up first paragraph so it looks better at crate-level summary
Adds `#[rustc_force_inline]` which is similar to always inlining but
reports an error if the inlining was not possible, and which always
attempts to inline annotated items, regardless of optimisation levels.
It can only be applied to free functions to guarantee that the MIR
inliner will be able to resolve calls.
