Auto merge of #65182 - anp:reify-shim, r=eddyb

Auto merge of #65182 - anp:reify-shim, r=eddyb

Add `Instance::resolve_for_fn_ptr` (RFC 2091 #2/N)

Supercedes: https://github.com/rust-lang/rust/pull/65082
Depends on: https://github.com/rust-lang/rust/pull/65037
Tracking issue: https://github.com/rust-lang/rust/issues/47809
[RFC text](https://github.com/rust-lang/rfcs/blob/master/text/2091-inline-semantic.md)

steps taken:

* [x] add a `ReifyShim` that is similar to `VirtualShim` in behavior (see #54183)
* [x] add `ty::Instance::resolve_for_fn_ptr` (leave `ty::Instance::resolve_vtable` alone), migrate appropriate callers
* [x] `resolve_for_fn_ptr` returns the shim if calling a `#[track_caller]` function