Clean up trivial traversal/lift impl generator macro calls.

We have four macros for generating trivial traversal (fold/visit) and
lift impls.
- `rustc_ir::TrivialTypeTraversalImpls`
- `rustc_middle::TrivialTypeTraversalImpls`
- `rustc_middle::TrivialLiftImpls`
- `rustc_middle::TrivialTypeTraversalAndLiftImpls`

The first two are very similar. The last one just combines the second
and third one.

The macros themselves are ok, but their use is a mess. This commit does
the following.
- Removes types that no longer need a lift and/or traversal impl from
  the macro calls.
- Consolidates the macro calls into the smallest number of calls
  possible, with each one mentioning as many types as possible.
- Orders the types within those macro calls alphabetically, and makes
  the module qualification more consistent.
- Eliminates `rustc_middle::mir::type_foldable`, because the macro calls
  were merged and the manual `TypeFoldable` impls are better placed in
  `structural_impls.rs`, alongside all the other ones.

This makes the code more concise. Moving forward, it also makes it more
obvious where new types should be added.

0 files changed, 0 insertions, 0 deletions