Added implementations for get_agents_session, delete_agents_session and delete_agents

[cheesecake100201]

Added implementations for not implemented methods for agents

[cheesecake100201]

Thank you. I have some minor comments. It would be good to add a test or two? See the tests in providers/tests/agents/test_agents.py -- I would suggest making another file for just testing agent persistence (which is what this PR mostly targets.)

Will make another PR for that if thats okay with you. And what I need to test is deleting session and agent, and getting turns and steps. Please do add whatever else is needed to be tested

[cheesecake100201]

Made formatting changes shown in pre-commit @ashwinb

[ashwinb]

Merged, thanks!