Propagate Log Level Override

[oxinabox]

This fixes the broken test for using with_level on top of a compositional logger.

I had hoped there was something we were doing wrong in the compositional components,
the fixing of which would make this all work elegantly.
But there is not.¹

So instead this takes the brute force approach of recursively reconstructing the logging stack. (well tree)
Luckily there is only a very finite number of logging types we will ever have so we can just handle each case.

TODO:

• More tests
• Think about if we can ever stop propagating early based on min_enabled_level (I don't think we can)

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¹ I have noted before this compositional loggers feels like how logging in julia should work, but it does not get a clean implementation, for julia 2.0 we should change Logging some how, including incorperating compositional logging into the stdlib, and removing inpure sinks.)

[quinnj]

• Think about if we can ever stop propagating early based on min_enabled_level (I don't think we can)

I agree that I don't think this is possible w/ current Base.CoreLogging logic. The problem is the call to get_current_env_logger does the min_enabled_level check before we even get to see what the current logger is, so there's no chance to overload, it's just a static check on the min_enabled_level when the logger was set.

We should probably start a document around proposals for 2.0 CoreLogging improvements. I've got a few thoughts as I've been digging around a bunch. It'd be nice to get it all cleaned up.

[oxinabox]

shall i rebase and merge this, or should i add more tests?

[quinnj]

Sorry, I've been on vacation the last 2 weeks. If it's alright, I'll try to circle back to this in the next few days, if we're ok waiting. I need to re-immerse myself with some of the logging stuff I was doing to get back in context.