Move some utils out of rustc_const_eval

This allows us to get rid of the `rustc_const_eval->rustc_borrowck`
dependency edge which was delaying the compilation of borrowck.

The added utils in `rustc_middle` are small and should not affect
compile times there.

compiler/rustc_mir_transform/src/check_const_item_mutation.rs

@@ -134,7 +134,12 @@ impl<'tcx> Visitor<'tcx> for ConstMutationChecker<'_, 'tcx> {
                 // the `self` parameter of a method call (as the terminator of our current
                 // BasicBlock). If so, we emit a more specific lint.
                 let method_did = self.target_local.and_then(|target_local| {
-                    crate::util::find_self_call(self.tcx, &self.body, target_local, loc.block)
+                    rustc_middle::util::find_self_call(
+                        self.tcx,
+                        &self.body,
+                        target_local,
+                        loc.block,
+                    )
                 });
                 let lint_loc =
                     if method_did.is_some() { self.body.terminator_loc(loc.block) } else { loc };