Refactor the code to initialize event loop only from async functions

[MrNaif2018]

The time has come. Python 3.10 is released which means that our old ways won't work, and new event loop would be created always.
Recently our tests got broken because of fastapi 0.69.0 release, which uses anyio. We had many issues with too many concurrent operations in progress because of event loop mismatch, and are using some workarounds in pytest-asyncio to make everything use same event loop:
https://github.com/bitcartcc/bitcart/blob/ac129fae929d0853137d327762ef7750537627b6/tests/conftest.py#L32-L34
https://github.com/bitcartcc/bitcart/blob/ac129fae929d0853137d327762ef7750537627b6/tests/conftest.py#L38
https://github.com/bitcartcc/bitcart/blob/ac129fae929d0853137d327762ef7750537627b6/tests/conftest.py#L44

SDK might need to be refactored as well. settings.py should be refactored to a class, most initialization might be moved to other files, possibly Worker class could be introduced to initialize worker.py. Adding new scheduled tasks system could be refactored as well.
redis pool and other connections need to be created on startup from async functions, not on import. Test suite workarounds should be removed and it should just work
If everything works then we can probably remove asyncio.get_event_loop().run_until_complete in favour of asyncio.run

[MrNaif2018]

Making this a release blocker because when upgrading the packages, uvicorn now uses asyncio.run for each connection, so events look don't match and SDK fails to work because it has saved event loop during module imports.
It was not noticed in tests but only after manual git bisect'ing and reading changelog of all packages
Any help welcome because for now I have no clue on how to do it properly without making developer experience worse

[MrNaif2018]

There are still some issues and fastapi upgrade pending
Regtest tests seems to be failing more frequently than before after #254

[MrNaif2018]

This has been implemented. Further testing is required

[MrNaif2018]

This seems to work fine. If some bugs occur after further user testing those can be fixed separately