Auto merge of #123781 - RalfJung:miri-fn-identity, r=oli-obk

Miri function identity hack: account for possible inlining

Having a non-lifetime generic is not the only reason a function can be duplicated. Another possibility is that the function may be eligible for cross-crate inlining. So also take into account the inlining attribute in this Miri hack for function pointer identity.

That said, `cross_crate_inlinable` will still sometimes return true even for `inline(never)` functions:
- when they are `DefKind::Ctor(..) | DefKind::Closure` -- I assume those cannot be `InlineAttr::Never` anyway?
- when `cross_crate_inline_threshold == InliningThreshold::Always`

so maybe this is still not quite the right criterion to use for function pointer identity.

compiler/rustc_codegen_gcc/src/common.rs

@@ -220,7 +220,7 @@ impl<'gcc, 'tcx> ConstMethods<'tcx> for CodegenCx<'gcc, 'tcx> {
                         }
                         value
                     }
-                    GlobalAlloc::Function(fn_instance) => self.get_fn_addr(fn_instance),
+                    GlobalAlloc::Function { instance, .. } => self.get_fn_addr(instance),
                     GlobalAlloc::VTable(ty, trait_ref) => {
                         let alloc = self
                             .tcx