fix(alembic): Making Alembic logger config optional

[craig-rueda]

SUMMARY

The default Alembic env.py file explicitly loads its own logger configuration, which overwrites any other settings that users may have set elsewhere. This PR adds an optional envvar that can be used to disable this behavior.

[codecov]

Codecov Report

Merging #17774 (54a9331) into master (71e4131) will decrease coverage by 0.00%.
The diff coverage is 33.33%.

@@            Coverage Diff             @@
##           master   #17774      +/-   ##
==========================================
- Coverage   67.71%   67.71%   -0.01%     
==========================================
  Files        1605     1605              
  Lines       64198    64200       +2     
  Branches     6790     6790              
==========================================
+ Hits        43474    43475       +1     
- Misses      18868    18869       +1     
  Partials     1856     1856              

Flag	Coverage Δ
hive	81.79% <33.33%> (-0.01%)	⬇️
mysql	82.17% <33.33%> (-0.01%)	⬇️
postgres	82.22% <33.33%> (-0.01%)	⬇️
python	82.56% <33.33%> (-0.01%)	⬇️
sqlite	81.90% <33.33%> (-0.01%)	⬇️

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Impacted Files	Coverage Δ
superset/migrations/env.py	0.00% <0.00%> (ø)
superset/config.py	91.63% <100.00%> (+0.02%)	⬆️

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