Auto merge of #117908 - lcnr:region-kind-rename, r=BoxyUwU

finish `RegionKind` renaming

second step of rust-lang/types-team#95

continues the work from #117876. While working on this and I encountered a bunch of further cleanup which I'll either open a tracking issue for or will do in a separate PR:
- rewrite the `RegionKind` docs, they still talk about `ReEmpty` and are generally out of date
- rename `DescriptionCtx` to `DescriptionCtxt`
- what is `CheckRegions::Bound`?
- `collect_late_bound_regions` et al
- `erase_late_bound_regions` -> `instantiate_bound_regions_with_erased`?
- `EraseEarlyRegions` visitor should be removed, feels duplicate

r? `@BoxyUwU`

Author: bors

clippy_lints/src/pass_by_ref_or_value.rs

@@ -175,7 +175,7 @@ impl<'tcx> PassByRefOrValue {
                         },
                         // Early bound regions on functions are either from the containing item, are bounded by another
                         // lifetime, or are used as a bound for a type or lifetime.
-                        RegionKind::ReEarlyBound(..) => continue,
+                        RegionKind::ReEarlyParam(..) => continue,
                         _ => (),
                     }
 

clippy_lints/src/ptr.rs

@@ -465,9 +465,9 @@ fn check_fn_args<'cx, 'tcx: 'cx>(
                                     .walk()
                                     .filter_map(|arg| {
                                         arg.as_region().and_then(|lifetime| match lifetime.kind() {
-                                            ty::ReEarlyBound(r) => Some(r.def_id),
+                                            ty::ReEarlyParam(r) => Some(r.def_id),
                                             ty::ReBound(_, r) => r.kind.get_id(),
-                                            ty::ReFree(r) => r.bound_region.get_id(),
+                                            ty::ReLateParam(r) => r.bound_region.get_id(),
                                             ty::ReStatic
                                             | ty::ReVar(_)
                                             | ty::RePlaceholder(_)