gh-103763: Implement PEP 695 (#103764)

This implements PEP 695, Type Parameter Syntax. It adds support for:

- Generic functions (def func[T](): ...)
- Generic classes (class X[T](): ...)
- Type aliases (type X = ...)
- New scoping when the new syntax is used within a class body
- Compiler and interpreter changes to support the new syntax and scoping rules 

Co-authored-by: Marc Mueller <30130371+cdce8p@users.noreply.github.com>
Co-authored-by: Eric Traut <eric@traut.com>
Co-authored-by: Larry Hastings <larry@hastings.org>
Co-authored-by: Alex Waygood <Alex.Waygood@Gmail.com>

Parser/Python.asdl

@@ -8,14 +8,15 @@ module Python
         | Expression(expr body)
         | FunctionType(expr* argtypes, expr returns)
 
-    stmt = FunctionDef(identifier name, arguments args,
+    stmt = FunctionDef(identifier name, typeparam* typeparams, arguments args,
                        stmt* body, expr* decorator_list, expr? returns,
                        string? type_comment)
-          | AsyncFunctionDef(identifier name, arguments args,
+          | AsyncFunctionDef(identifier name, typeparam* typeparams, arguments args,
                              stmt* body, expr* decorator_list, expr? returns,
                              string? type_comment)
 
           | ClassDef(identifier name,
+             typeparam* typeparams,
              expr* bases,
              keyword* keywords,
              stmt* body,
@@ -24,6 +25,7 @@ module Python
 
           | Delete(expr* targets)
           | Assign(expr* targets, expr value, string? type_comment)
+          | TypeAlias(expr name, typeparam* typeparams, expr value)
           | AugAssign(expr target, operator op, expr value)
           -- 'simple' indicates that we annotate simple name without parens
           | AnnAssign(expr target, expr annotation, expr? value, int simple)
@@ -142,4 +144,9 @@ module Python
              attributes (int lineno, int col_offset, int end_lineno, int end_col_offset)
 
     type_ignore = TypeIgnore(int lineno, string tag)
+
+    typeparam = TypeVar(identifier name, expr? bound)
+            | ParamSpec(identifier name)
+            | TypeVarTuple(identifier name)
+             attributes (int lineno, int col_offset, int? end_lineno, int? end_col_offset)
 }