Remove in_band_lifetimes from rustc_middle

See #91867

This was mostly straightforward. In several places, I take advantage
of the fact that lifetimes are non-hygenic: a macro declares the
'tcx' lifetime, which is then used in types passed in as macro
arguments.

compiler/rustc_middle/src/lib.rs

@@ -44,7 +44,6 @@
 #![feature(let_else)]
 #![feature(min_specialization)]
 #![feature(trusted_len)]
-#![feature(in_band_lifetimes)]
 #![feature(crate_visibility_modifier)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]