DM-33870: Support repo aliases in Butler constructor

[timj]

Checklist

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

[codecov]

Codecov Report

Merging #654 (19addb8) into main (c999bd6) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #654   +/-   ##
=======================================
  Coverage   83.67%   83.67%           
=======================================
  Files         239      239           
  Lines       30362    30377   +15     
  Branches     5087     5089    +2     
=======================================
+ Hits        25404    25419   +15     
  Misses       3805     3805           
  Partials     1153     1153           

Impacted Files	Coverage Δ
python/lsst/daf/butler/_butler.py	81.02% <100.00%> (+0.26%)	⬆️
tests/test_butler.py	97.71% <100.00%> (+0.01%)	⬆️

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[andy-slac]

Looks good, couple of minor comments.