Rename logging modules to be private

[mdekstrand]

This makes the logging submodules private, which is the last set of private submodules. Closes #947.

[codecov]

Codecov Report

❌ Patch coverage is 95.45455% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 89.48%. Comparing base (992c791) to head (ea71939).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/lenskit/logging/tasks.py	80.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1070      +/-   ##
==========================================
+ Coverage   89.46%   89.48%   +0.02%     
==========================================
  Files         233      231       -2     
  Lines       15874    15867       -7     
==========================================
- Hits        14201    14199       -2     
+ Misses       1673     1668       -5     

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