Update logging configuration

[jonathangreen]

Description

Two changes to our logging configuration:

• Update the LogLevel Enum to be a StrEnum, so it is easy to use the values from this enum to directly configure logging.
• Update our logging handler creation to not set a log level.
  • We were setting the level on both the handlers, and on the logger itself. This is unnecessary, and makes it harder to update our log level when using celery.
  • This functionally doesn't change anything, since the log level is being controlled by the logger.

Motivation and Context

These changes were needed when configuring logging for Celery in #1760, but they stand on their own, and I think it makes sense for them to go in separately to simplify that PR.

How Has This Been Tested?

Running tests in CI.

Checklist

• I have updated the documentation accordingly.
• All new and existing tests passed.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 90.24%. Comparing base (75c30c0) to head (5d3b1bb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1775   +/-   ##
=======================================
  Coverage   90.23%   90.24%           
=======================================
  Files         247      247           
  Lines       28327    28346   +19     
  Branches     6462     6467    +5     
=======================================
+ Hits        25561    25580   +19     
  Misses       1829     1829           
  Partials      937      937           

Flag	Coverage Δ
Api	75.77% <67.85%> (-0.01%)	⬇️
Core	59.47% <96.42%> (+0.02%)	⬆️
migration	24.12% <64.28%> (+0.02%)	⬆️

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[tdilauro]

Looks good! 🎺

[tdilauro]

Minor: Can we move these up under the docstring, so that they are the most visible when looking at the class?

[jonathangreen]

Unfortunately _generate_next_value_ has to be defined before any members.

https://docs.python.org/3/howto/enum.html#using-automatic-values