➖ remove asynctest dependency and replace with unittest

[ff137]

Replaces asynctest with unittest in all modules

Includes formatting changes from #448. Marking as draft until that one's merged

[ff137]

For some reason the relay image in redis-events was bumped to pydantic 2, causing the prev test failures. Resolved this by pinning pydantic <2 in redis-events/docker/services/

[ff137]

This one's probably harder to review, but it's all in the 3f7a901 commit!

To help summarise: all of the asynctest imports can essentially be swapped to unittest.
So we had from asynctest import mock as async_mock, and then everywhere that async_mock.MagicMock is used, that can be swapped for unittest.MagicMock. Same with patch, AsyncMock, etc.

Lastly, AsyncTestCase is now IsolatedAsyncioTestCase, and the setUp method had to be renamed to asyncSetUp.
That's it! Works like a charm.

Main motivation is not wanting deprecated dependencies, but also to get the testing framework in sync with ACA-Py (as in openwallet-foundation/acapy#2566 and openwallet-foundation/acapy#2755), helps with maintainability across the repos