Rollup merge of #127136 - compiler-errors:coroutine-closure-env-shim, r=oli-obk

Fix `FnMut::call_mut`/`Fn::call` shim for async closures that capture references

I adjusted async closures to be able to implement `Fn` and `FnMut` *even if* they capture references, as long as those references did not need to borrow data from the closure captures themselves. See #125259.

However, when I did this, I didn't actually relax an assertion in the `build_construct_coroutine_by_move_shim` shim code, which builds the `Fn`/`FnMut`/`FnOnce` implementations for async closures. Therefore, if we actually tried to *call* `FnMut`/`Fn` on async closures, it would ICE.

This PR adjusts this assertion to ensure that we only capture immutable references in closures if they implement `Fn`/`FnMut`. It also adds a bunch of tests and makes more of the async-closure tests into `build-pass` since we often care about these tests actually generating the right closure shims and stuff. I think it might be excessive to *always* use build-pass here, but 🤷 it's not that big of a deal.

Fixes #127019
Fixes #127012

r? oli-obk

compiler/rustc_codegen_ssa/src/mir/locals.rs

@@ -47,7 +47,7 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
                     let expected_ty = self.monomorphize(self.mir.local_decls[local].ty);
                     if expected_ty != op.layout.ty {
                         warn!(
-                            "Unexpected initial operand type: expected {expected_ty:?}, found {:?}.\
+                            "Unexpected initial operand type:\nexpected {expected_ty:?},\nfound    {:?}.\n\
                             See <https://github.com/rust-lang/rust/issues/114858>.",
                             op.layout.ty
                         );