Rollup merge of #128453 - RalfJung:raw_eq, r=saethlin

raw_eq: using it on bytes with provenance is not UB (outside const-eval)

The current behavior of raw_eq violates provenance monotonicity. See https://github.com/rust-lang/rust/pull/124921 for an explanation of provenance monotonicity. It is violated in raw_eq because comparing bytes without provenance is well-defined, but adding provenance makes the operation UB.

So remove the no-provenance requirement from raw_eq. However, the requirement stays in-place for compile-time invocations of raw_eq, that indeed cannot deal with provenance.

Cc `@rust-lang/opsem`

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -690,9 +690,6 @@ impl<'tcx, M: Machine<'tcx>> InterpCx<'tcx, M> {
                 // zero-sized access
                 return Ok(&[]);
             };
-            if alloc_ref.has_provenance() {
-                throw_ub_custom!(fluent::const_eval_raw_eq_with_provenance);
-            }
             alloc_ref.get_bytes_strip_provenance()
         };