implement rust-lang/types-team#78

Change all queries which currently have a bound_X variant to return EarlyBinder<T> by default and remove the bound_X version. Add a method fn EarlyBinder::<T>::subst_identity(self) -> T if these queries are used in the identity context and don't need to actually substitute anything.

Not having EarlyBinder be the default can very easily result in incorrect uses of these queries, e.g.

rust/compiler/rustc_hir_analysis/src/astconv/mod.rs

Line 2720 in 736c675

EarlyBinder(self.normalize_ty(span, tcx.at(span).type_of(def_id)))

which I found while reviewing #101947. The normalize_ty normalizes type_of(def_id) in the wrong environment as we only call subst afterwards.