Remove NtTy.

Notes about tests:

- tests/ui/parser/macro/trait-object-macro-matcher.rs: the syntax error
  is duplicated, because it occurs now when parsing the decl macro
  input, and also when parsing the expanded decl macro. But this won't
  show up for normal users due to error de-duplication.

- tests/ui/associated-consts/issue-93835.rs: similar, plus there are
  some additional errors about this very broken code.

- The changes to metavariable descriptions in #132629 are now visible in
  error message for several tests.

compiler/rustc_ast/src/token.rs

@@ -659,7 +659,6 @@ impl Token {
                     | NtMeta(..)
                     | NtPat(..)
                     | NtPath(..)
-                    | NtTy(..)
                 ),
             OpenDelim(Delimiter::Invisible(InvisibleOrigin::MetaVar(
                 MetaVarKind::Expr { .. } |
@@ -688,7 +687,7 @@ impl Token {
             Lifetime(..)                | // lifetime bound in trait object
             Lt | BinOp(Shl)             | // associated path
             PathSep                      => true, // global path
-            Interpolated(ref nt) => matches!(&**nt, NtTy(..) | NtPath(..)),
+            Interpolated(ref nt) => matches!(&**nt, NtPath(..)),
             OpenDelim(Delimiter::Invisible(InvisibleOrigin::MetaVar(
                 MetaVarKind::Ty |
                 MetaVarKind::Path
@@ -1076,7 +1075,6 @@ pub enum Nonterminal {
     NtStmt(P<ast::Stmt>),
     NtPat(P<ast::Pat>),
     NtExpr(P<ast::Expr>),
-    NtTy(P<ast::Ty>),
     NtLiteral(P<ast::Expr>),
     /// Stuff inside brackets for attributes
     NtMeta(P<ast::AttrItem>),
@@ -1174,7 +1172,6 @@ impl Nonterminal {
             NtStmt(stmt) => stmt.span,
             NtPat(pat) => pat.span,
             NtExpr(expr) | NtLiteral(expr) => expr.span,
-            NtTy(ty) => ty.span,
             NtMeta(attr_item) => attr_item.span(),
             NtPath(path) => path.span,
         }
@@ -1188,7 +1185,6 @@ impl Nonterminal {
             NtPat(..) => "pattern",
             NtExpr(..) => "expression",
             NtLiteral(..) => "literal",
-            NtTy(..) => "type",
             NtMeta(..) => "attribute",
             NtPath(..) => "path",
         }
@@ -1213,7 +1209,6 @@ impl fmt::Debug for Nonterminal {
             NtStmt(..) => f.pad("NtStmt(..)"),
             NtPat(..) => f.pad("NtPat(..)"),
             NtExpr(..) => f.pad("NtExpr(..)"),
-            NtTy(..) => f.pad("NtTy(..)"),
             NtLiteral(..) => f.pad("NtLiteral(..)"),
             NtMeta(..) => f.pad("NtMeta(..)"),
             NtPath(..) => f.pad("NtPath(..)"),