Fix some logging issues

[Radiokot]

Hey guys,

This pull request addresses some logging issues I spotted long ago, but today I wanted to have certain PowerSync logs in my common app log, and this was time to fix them.

1. Fixed modifying severity of the global Kermit logger – it is up to the app owner to decide on this parameter. The library no longer uses the global instance by default;
2. Added PowerSync tag to the logs – as now the library has its own default logger instance, it deserves a tag;
3. Removed generateLogger() global public method – it really seemed like a method meant to be used internally as it is quite specific, but even internally it is no longer needed.

I didn't run any tests because I couldn't wait for the project to build. On my Intel Core Ultra 7 14x4.8 GHz with 32 GB of RAM the build didn't finish in 45 minutes, it's already late here and I should go to bed soon.

[Radiokot]

Ok, seems that I shouldn't try to beat this lint without support from IDEA, but it doesn't work until the project is built, which it doesn't.