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/const_debuginfo.rs

@@ -89,7 +89,7 @@ fn find_optimization_oportunities<'tcx>(body: &Body<'tcx>) -> Vec<(Local, Consta
     eligable_locals
 }
 
-impl<'tcx> Visitor<'tcx> for LocalUseVisitor {
+impl Visitor<'_> for LocalUseVisitor {
     fn visit_local(&mut self, local: &Local, context: PlaceContext, location: Location) {
         if context.is_mutating_use() {
             self.local_mutating_uses[*local] = self.local_mutating_uses[*local].saturating_add(1);