Make micropython.const accept any constant type

micropython.const now supports any constant type, not just int. This
updates the type checking to reflect this. This also updates the name of
the file so that type checkers can find it.

Author: dunkmann00

src/micropython-stubs/micropython.pyi renamed to src/micropython-stubs/__init__.pyi

@@ -12,7 +12,7 @@ from typing import Callable, TypeVar, Any, NoReturn
 
 Fun = TypeVar("Fun", bound=Callable[..., Any])
 
-def const(x: int) -> int:
+def const[T](x: T) -> T:
     "Emulate making a constant"
 
 def native(f: Fun) -> Fun: