Auto merge of #108340 - eggyal:remove_traversal_trait_aliases, r=oli-obk

Remove type-traversal trait aliases

#107924 moved the type traversal (folding and visiting) traits into the type library, but created trait aliases in `rustc_middle` to minimise both the API churn for trait consumers and the arising boilerplate.  As mentioned in that PR, an alternative approach of defining subtraits with blanket implementations of the respective supertraits was also considered at that time but was ruled out as not adding much value.

Unfortunately, it has since emerged that rust-analyzer has difficulty with these trait aliases at present, resulting in a degraded contributor experience (see the recent [r-a has become useless](https://rust-lang.zulipchat.com/#narrow/stream/182449-t-compiler.2Fhelp/topic/r-a.20has.20become.20useless) topic on the #t-compiler/help Zulip stream).

This PR removes the trait aliases, and accordingly the underlying type library traits are now used directly; they are parameterised by `TyCtxt<'tcx>` rather than just the `'tcx` lifetime, and imports have been updated to reflect the fact that the trait aliases' explicitly named traits are no longer automatically brought into scope.  These changes also roll-back the (no-longer required) workarounds to #107747 that were made in b409329c624b9e3bbd7d8e07697e2e9f861a45b6.

Since this PR is just a find+replace together with the changes necessary for compilation & tidy to pass, it's currently just one mega-commit.  Let me know if you'd like it broken up.

r? `@oli-obk`

4 files changed, 6 insertions, 4 deletions

diff --git a/compiler/rustc_mir_transform/src/const_prop.rs b/compiler/rustc_mir_transform/src/const_prop.rs
index cff3da720fc..6b2eefce24d 100644
--- a/compiler/rustc_mir_transform/src/const_prop.rs
+++ b/compiler/rustc_mir_transform/src/const_prop.rs
@@ -16,7 +16,7 @@ use rustc_middle::mir::visit::{
 use rustc_middle::mir::*;
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::InternalSubsts;
-use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitable};
+use rustc_middle::ty::{self, ConstKind, Instance, ParamEnv, Ty, TyCtxt, TypeVisitableExt};
 use rustc_span::{def_id::DefId, Span};
 use rustc_target::abi::{self, Align, HasDataLayout, Size, TargetDataLayout};
 use rustc_target::spec::abi::Abi as CallAbi;
diff --git a/compiler/rustc_mir_transform/src/const_prop_lint.rs b/compiler/rustc_mir_transform/src/const_prop_lint.rs
index be41d611fe4..6c1980ff3ad 100644
--- a/compiler/rustc_mir_transform/src/const_prop_lint.rs
+++ b/compiler/rustc_mir_transform/src/const_prop_lint.rs
@@ -21,7 +21,9 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::layout::{LayoutError, LayoutOf, LayoutOfHelpers, TyAndLayout};
 use rustc_middle::ty::InternalSubsts;
-use rustc_middle::ty::{self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitable};
+use rustc_middle::ty::{
+    self, ConstInt, Instance, ParamEnv, ScalarInt, Ty, TyCtxt, TypeVisitableExt,
+};
 use rustc_session::lint;
 use rustc_span::Span;
 use rustc_target::abi::{HasDataLayout, Size, TargetDataLayout};
diff --git a/compiler/rustc_mir_transform/src/inline/cycle.rs b/compiler/rustc_mir_transform/src/inline/cycle.rs
index b027f94925d..792457c80b0 100644
--- a/compiler/rustc_mir_transform/src/inline/cycle.rs
+++ b/compiler/rustc_mir_transform/src/inline/cycle.rs
@@ -2,7 +2,7 @@ use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
 use rustc_data_structures::stack::ensure_sufficient_stack;
 use rustc_hir::def_id::{DefId, LocalDefId};
 use rustc_middle::mir::TerminatorKind;
-use rustc_middle::ty::TypeVisitable;
+use rustc_middle::ty::TypeVisitableExt;
 use rustc_middle::ty::{self, subst::SubstsRef, InstanceDef, TyCtxt};
 use rustc_session::Limit;
 
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs
index 45cd4024c9f..bdd1e8fb98f 100644
--- a/compiler/rustc_mir_transform/src/lib.rs
+++ b/compiler/rustc_mir_transform/src/lib.rs
@@ -35,7 +35,7 @@ use rustc_middle::mir::{
     TerminatorKind,
 };
 use rustc_middle::ty::query::Providers;
-use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
+use rustc_middle::ty::{self, TyCtxt, TypeVisitableExt};
 use rustc_span::sym;
 
 #[macro_use]