Fix a bug in the opt-in-copy work: it was failing to liberate the regions bound in...

Fix a bug in the opt-in-copy work: it was failing to liberate the regions bound in the impl before searching for `Copy` implements for all fields, leading to problems in the "copyability check". Basically the copyability check would wind up looking for an impl of `for<'tcx> Foo<&'tcx T>`. The impl that exists however is `impl<T> Copy for Foo<T>` and the current rules do not consider that a match (something I would like to revise in a later PR).