DM-32142: Add logging.trace_set_at

[timj]

Checklist

• ran Jenkins
• added a release note for user-visible changes to doc/changes

[codecov]

Codecov Report

Merging #102 (291cc6f) into master (e7cdf9e) will increase coverage by 0.10%.
The diff coverage is 100.00%.

❗ Current head 291cc6f differs from pull request most recent head 5effe52. Consider uploading reports for the commit 5effe52 to get more accurate results

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
+ Coverage   90.80%   90.90%   +0.10%     
==========================================
  Files          36       36              
  Lines        2087     2111      +24     
==========================================
+ Hits         1895     1919      +24     
  Misses        192      192              

Impacted Files	Coverage Δ
python/lsst/utils/logging.py	81.63% <100.00%> (+1.19%)	⬆️
tests/test_logging.py	98.18% <100.00%> (+0.88%)	⬆️

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[ktlim]

You might also confirm what happens if you do trace_set_at("lsst", 2) but look at getLogger("TRACE3.lsst.afw").getEffectiveLevel(). Since we're now having loggers start with lsst, there shouldn't be a need to support trace_set_at("", ...).