Set logger parents and levels

[pamelafox]

This is my proposal for handling levels in the logger hierarchy in a way which doesn't require parent traversal on every logging call.

This PR adds two new properties to Logger: effective_level and children. The effective_level is based on the level of the parents, or is equal to level if that's explicitly set with setLevel. When setLevel is called on a logger with children, then that level becomes the effective_level of any child with a level of NOT_SET.

I believe it is necessary to keep track of both level and effective_level so that we know which children's effective levels would be affected by a parent change.

Let me know what you think of this approach.

[codecov-commenter]

Codecov Report

Merging #108 (2180ca3) into main (de33c22) will increase coverage by 0.10%.
The diff coverage is 98.71%.

❗ Current head 2180ca3 differs from pull request most recent head 55f70e8. Consider uploading reports for the commit 55f70e8 to get more accurate results

@@            Coverage Diff             @@
##             main     #108      +/-   ##
==========================================
+ Coverage   88.83%   88.94%   +0.10%     
==========================================
  Files          11       11              
  Lines        2069     2098      +29     
==========================================
+ Hits         1838     1866      +28     
- Misses        231      232       +1     

Impacted Files	Coverage Δ
src/picologging/logger.cxx	84.50% <97.50%> (-0.66%)	⬇️
src/picologging/__init__.py	93.98% <100.00%> (+1.28%)	⬆️

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[pamelafox]

I'm adding additional tests, the C code isn't quite right yet.

[tonybaloney]

I like the approach, it seems clean and shouldn't really impact the performance of the critical path.

In the tests, it'll be important to use docstrings to describe the setup of the test, e.g.:

def test_scenario_1():
   """
  Before: 

   root - 100
    -- child 1 (NOTSET) - effective 100
    -- child 2 (200) - effective 200

  After:
   root - 200
    -- child 1 (NOTSET) - effective 200
    -- child 2 (200) - effective 300?
   """

[tonybaloney]

If you write a detailed docstring like that, Github copilot will probably write the test for you as well :-)

[pamelafox]

I just ran the tests from the CPython test_logging.py file that I had previously marked as unable to pass due to lack of hierarchy support, and they all pass! I could add the CPython tests here, but I think my current tests are pretty good coverage.
I added in the docstrings as well.
Let me know if you'd like any other changes!

[pamelafox]

TODO:

• Increase code coverage
• PlaceHolder -> _Placeholder
• Run memray tests / add another if needed