coercions reviews/misc whatevers

[BoxyUwU]

Fixes #132765 "remove normalize call" in theory breaking as we might now treat some previously-ambig hr aliases as rigid when we shouldn't. we may want to explicitly normalize the coercion target in fcx.coerce like the new solver does

wip misc stuff from while i'm reviewing/reading through this logic

r? ghost

[rust-log-analyzer]

The job tidy failed! Check out the build log: (web) (plain enhanced) (plain)

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##[endgroup]
[TIMING:end] tool::ToolBuild { build_compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu, tool: "tidy", path: "src/tools/tidy", mode: ToolBootstrap, source_type: InTree, extra_features: [], allow_features: "", cargo_args: [], artifact_kind: Binary } -- 12.118
[TIMING:end] tool::Tidy { compiler: Compiler { stage: 0, host: x86_64-unknown-linux-gnu, forced_compiler: false }, target: x86_64-unknown-linux-gnu } -- 0.000
fmt check
Diff in /checkout/compiler/rustc_hir_typeck/src/coercion.rs:356:
             let coercion = RegionVariableOrigin::Coercion(self.cause.span);
             let r_borrow = self.next_region_var(coercion);
             let autorefd_deref_ty = Ty::new_ref(self.tcx, r_borrow, deref_ty, mutbl_b);
-            
+
             // Note that we unify the autoref'd `Target` type with `b` rather than
             // the `Target` type with the pointee of `b`. This is necessary
             // to properly account for the differing variances of the pointees
fmt: checked 6467 files
Bootstrap failed while executing `test src/tools/tidy tidyselftest --extra-checks=py,cpp,js,spellcheck`
Build completed unsuccessfully in 0:00:48
  local time: Fri Oct 10 23:41:51 UTC 2025