Rework `feature(precise_capturing)` to represent `use<...>` as a syntactical bound
Reworks `precise_capturing` for a recent lang-team consensus.
Specifically:
> The conclusion of the team is that we'll make use<..> a bound. That is, we'll support impl use<..> + Trait, impl Trait + use<..>, etc.
> For now, we will support at most one such bound in a list of bounds, and semantically we'll only support these bounds in the item bounds of RPIT-like impl Trait opaque types (i.e., in the places discussed in the RFC).
Lang decision in favor of this approach:
- https://github.com/rust-lang/rust/issues/125836#issuecomment-2151351849
Tracking:
- https://github.com/rust-lang/rust/issues/123432
c1f62a7c35