Rename some things related to literals.

- Rename `ast::Lit::token` as `ast::Lit::token_lit`, because its type is
  `token::Lit`, which is not a token. (This has been confusing me for a
  long time.)
  reasonable because we have an `ast::token::Lit` inside an `ast::Lit`.
- Rename `LitKind::{from,to}_lit_token` as
  `LitKind::{from,to}_token_lit`, to match the above change and
  `token::Lit`.

compiler/rustc_ast_lowering/src/lib.rs

@@ -928,7 +928,7 @@ impl<'a, 'hir> LoweringContext<'a, 'hir> {
                     lit.clone()
                 } else {
                     Lit {
-                        token: token::Lit::new(token::LitKind::Err, kw::Empty, None),
+                        token_lit: token::Lit::new(token::LitKind::Err, kw::Empty, None),
                         kind: LitKind::Err(kw::Empty),
                         span: DUMMY_SP,
                     }