qa: cleanup MLflow

[aarnphm]

Cleanup some logic, qa with local postgres, mysql setup of mlflow registry.
cleanup some types as well.

[codecov]

Codecov Report

Merging #2945 (7d208e9) into main (d3d9cdb) will increase coverage by 1.61%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #2945      +/-   ##
==========================================
+ Coverage   68.99%   70.60%   +1.61%     
==========================================
  Files         122      104      -18     
  Lines       10131     9564     -567     
==========================================
- Hits         6990     6753     -237     
+ Misses       3141     2811     -330     

Impacted Files	Coverage Δ
bentoml/_internal/frameworks/mlflow.py	91.42% <100.00%> (-0.13%)	⬇️
bentoml/_internal/frameworks/torchscript.py	0.00% <0.00%> (-96.00%)	⬇️
bentoml/_internal/frameworks/common/pytorch.py	0.00% <0.00%> (-72.64%)	⬇️
bentoml/_internal/runner/strategy.py	83.05% <0.00%> (-8.48%)	⬇️
bentoml/_internal/runner/runner_handle/local.py	76.00% <0.00%> (-8.00%)	⬇️
bentoml/_internal/frameworks/keras.py	84.25% <0.00%> (-5.84%)	⬇️
bentoml/_internal/server/runner_app.py	95.32% <0.00%> (-2.64%)	⬇️
bentoml/_internal/models/model.py	88.41% <0.00%> (-1.66%)	⬇️
bentoml/_internal/runner/runner.py	90.90% <0.00%> (-0.91%)	⬇️
bentoml/_internal/utils/analytics/usage_stats.py	96.42% <0.00%> (ø)
... and 22 more