[OAS3] Schemas Generator minor improvements

[peppelinux]

Better generalization for third-party integrations.

Added **kwargs in schema contructors and related callables that initialize it. The goal: have a better generalization for third-party schema generators that would need more arguments in BaseGenerator. init

Derived from this: https://github.com/encode/django-rest-framework/pull/7461

[stale[bot]]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[lovelydinosaur]

We should probably let this be closed, right?