Allow group members handling from any auth provider for local groups

[fpfuetsch]

Description

This PR allows getting / adding / deleting members from any auth provider to local groups by removing the provider (="local") filter.

GitHub Issues

Fixes #210

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, pep8, linting, or security issues
• I have performed Ansible Sanity test using --docker default
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• Backward compatibility is not broken

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

• Tested using local module build

[fpfuetsch]

@anupamaloke @ShrinidhiRao15 @gokul-srivathsan anybody there? 😶‍🌫️

[gokul-srivathsan]

@fpfuetsch , this PR merge requires further functional tests on Group module. Please expect some delay in further action.

[anupamaloke]

LGTM