Remove in_band_lifetimes from rustc_mir_transform

This one is a heavy `'tcx` user.

Two interesting ones:

This one had the `'tcx` declared on the function, despite the trait taking a `'tcx`:
```diff
-impl Visitor<'_> for UsedLocals {
+impl<'tcx> Visitor<'tcx> for UsedLocals {
     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
```

This one use in-band for one, and underscore for the other:
```diff
-pub fn remove_dead_blocks(tcx: TyCtxt<'tcx>, body: &mut Body<'_>) {
+pub fn remove_dead_blocks<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
```

compiler/rustc_mir_transform/src/shim.rs

@@ -247,7 +247,7 @@ pub struct DropShimElaborator<'a, 'tcx> {
     pub param_env: ty::ParamEnv<'tcx>,
 }
 
-impl<'a, 'tcx> fmt::Debug for DropShimElaborator<'a, 'tcx> {
+impl fmt::Debug for DropShimElaborator<'_, '_> {
     fn fmt(&self, _f: &mut fmt::Formatter<'_>) -> Result<(), fmt::Error> {
         Ok(())
     }
@@ -337,7 +337,7 @@ struct CloneShimBuilder<'tcx> {
     sig: ty::FnSig<'tcx>,
 }
 
-impl CloneShimBuilder<'tcx> {
+impl<'tcx> CloneShimBuilder<'tcx> {
     fn new(tcx: TyCtxt<'tcx>, def_id: DefId, self_ty: Ty<'tcx>) -> Self {
         // we must subst the self_ty because it's
         // otherwise going to be TySelf and we can't index