chore: move mark openapi spec to global module

[badayvedat]

To be used with the exposed_port apps, which we can not guarantee the order of the schema fields. With the _mark_order_openapi function we guarantee that the order will be preserved.

Example usage:

import fal
from fal.app import _mark_order_openapi

@fal.function(..., exposed_port=8080, metadata=_mark_order_openapi(openapi_spec))
def test():
    ...

[chamini2]

Nice!