Improve ast types; revert several "redundant numeric union" changes from #7906 (#9130)

* Adapt number types in ast

Since mypy  0.990 type promotions was limited.
This means that complex is not longer promoted to int/float, therefore
we should adapt the types to list all possible types

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: AlexWaygood <alex.waygood@gmail.com>

stdlib/_ast.pyi

@@ -329,7 +329,7 @@ class JoinedStr(expr):
 
 if sys.version_info < (3, 8):
     class Num(expr):  # Deprecated in 3.8; use Constant
-        n: complex
+        n: int | float | complex
 
     class Str(expr):  # Deprecated in 3.8; use Constant
         s: str
@@ -349,7 +349,7 @@ class Constant(expr):
     kind: str | None
     # Aliases for value, for backwards compatibility
     s: Any
-    n: complex
+    n: int | float | complex
 
 if sys.version_info >= (3, 8):
     class NamedExpr(expr):