core: allow const() values to have Literal type

core/mocks/micropython.pyi

@@ -1,4 +1,8 @@
-def const(c: int) -> int: ...
+from typing import TypeVar
+
+C = TypeVar("C", bound=int)
+
+def const(c: C) -> C: ...
 def mem_info() -> None: ...
 def mem_current() -> int: ...
 def mem_total() -> int: ...