Clean up `ty::Dynamic`

1. As a follow-up to PR rust-lang/rust#143036, remove `DynKind` entirely.
2. Inside HIR ty lowering, consolidate modules `dyn_compatibility` and `lint` into `dyn_trait`
   * `dyn_compatibility` wasn't about dyn compatibility itself, it's about lowering trait object types
   * `lint` contained dyn-Trait-specific diagnostics+lints only

…ubtree-update

Co-authored-by: Anne Stijns <[email protected]>

I.e. do not mark them as used, or non-speculative loaded, or similar.
Previously they were sometimes finalized during early resolution, causing issues like rust-lang/rust#144793 (comment).

Extended temporary argument to format_args!() in all cases

Fixes rust-lang/rust#145880 by removing the special case.

resolve: Do not finalize shadowed bindings

I.e. do not mark them as used, or non-speculatively loaded, or similar.
Previously they were sometimes finalized during early resolution, causing issues like rust-lang/rust#144793 (comment).

Bump bootstrap compiler to 1.91 beta

https://forge.rust-lang.org/release/process.html#default-branch-bootstrap-update-tuesday

Much of the compiler calls functions on Align projected from AbiAlign.
AbiAlign impls Deref to its inner Align, so we can simplify these away.
Also, it will minimize disruption when AbiAlign is removed.

For now, preserve usages that might resolve to PartialOrd or PartialEq,
as those have odd inference.

Turn ProjectionElem::Subtype into CastKind::Subtype

I noticed that drop elaboration can't, in general, handle `ProjectionElem::SubType`. It creates a disjoint move path that overlaps with other move paths. (`Subslice` does too, and I'm working on a different PR to make that special case less fragile.) If its skipped and treated as the same move path as its parent then `MovePath.place` has multiple possible projections. (It would probably make sense to remove all `Subtype` projections for the canonical place but it doesn't make sense to have this special case for a problem that doesn't actually occur in real MIR.)

The only reason this doesn't break is that `Subtype` is always the sole projection of the local its applied to. For the same reason, it works fine as a `CastKind` so I figured that makes more sense than documenting and validating this hidden invariant.

cc rust-lang/rust#112651, rust-lang/rust#133258

r? Icnr (bc you've been the main person dealing with `Subtype` it looks like)

Split Bound index into Canonical and Bound

See [#t-types/trait-system-refactor > perf &rust-lang#96;async-closures/post-mono-higher-ranked-hang.rs&rust-lang#96;](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/perf.20.60async-closures.2Fpost-mono-higher-ranked-hang.2Ers.60/with/541535613) for context

Things compile and tests pass, but not sure if this actually solves the perf issue (edit: it does). Opening up this to do a perf (and maybe crater) run.

r? lcnr