wip: refactor log sink

[j-g00da]

Closes: #8555

[j-g00da]

This is a draft, not really sure about any of this yet.
Few major issues which I still need to go through:

1. Removing messages from the channel using e.g. get_matching will cause some logs to not be printed or asserted.
2. Two tests are still flaky and need a timeout... I temporarily added sleep there.

[link2xt]

This can likely be fixed by join() for recently seen loop task before dropping recently_seen_loop, probably need some changes there so it can be shut down cleanly as outside the tests we currently just abort it from the scheduler.

[link2xt]

Not sure, but maybe this case can be fixed by inserting EventType::Test and then reading events until finding it in assert_warns_or_errors, similarly to what get_matching_ext does.

[link2xt]

nit: getters normally don't have a get_ prefix in rust (https://rust-lang.github.io/api-guidelines/naming.html#getter-names-follow-rust-convention-c-getter). I think we have it in several places anyway, also because of C conventions around FFI and older code.

[link2xt]

Removing messages from the channel using e.g. get_matching will cause some logs to not be printed or asserted.

This can likely be solved by creating another broadcast channel receiver and reading from it. Not as simple as expected originally, but will avoid the task (the one that was spawned in subscribe() method) copying events between channels asynchronously.