fix: allow reference sub-factories in SelfAttribute

[ADR-007]

BREAKING CHANGE:
AsyncSQLAlchemyFactory.build() and AsyncSQLAlchemyFactory.build_batch() now have to be awaited

[ADR-007]

The error doesn't look related to my changes:

      def finalizer() -> None:
          """
          Cleans up the DB after testing. Must be called as part of the test environment teardown.
          """
          _restore_default()
          loop = _LOOP
          loop._selector = _SELECTOR  # type: ignore
  >       loop.run_until_complete(Tortoise._drop_databases())

[FadingFog]

@ADR-007 Thanks for PR. Same issue with build_batch() method. Can you please fix this too?

[ADR-007]

@ADR-007 Thanks for PR. Same issue with the build_batch() method. Can you please fix this too?

Sure, but I'm quite busy now :(

[ADR-007]

@ADR-007 Thanks for PR. Same issue with build_batch() method. Can you please fix this too?

It should be good now :)

[FadingFog]

@kuzxnia Hi, can you review & merge this PR?