[Release] Revert quantization scheme StrEnum release

[nikita-savelyevv]

Copy of #2629 to release branch

[nikita-savelyevv]

PT nightly test build 185

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (release_v2100@8638ff0). Click here to learn what that means.

Additional details and impacted files

@@               Coverage Diff                @@
##             release_v2100    #2630   +/-   ##
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  Coverage                 ?   77.94%           
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  Files                    ?      494           
  Lines                    ?    45374           
  Branches                 ?        0           
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  Hits                     ?    35368           
  Misses                   ?    10006           
  Partials                 ?        0           

Files	Coverage Δ
nncf/common/quantization/structs.py	96.18% <100.00%> (ø)

Flag	Coverage Δ
TENSORFLOW	30.12% <100.00%> (?)
TORCH	65.95% <100.00%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
common	88.32% <0.00%> (?)
torch	93.48% <0.00%> (?)
tensorflow	93.74% <0.00%> (?)
onnx	0.00% <0.00%> (?)
openvino	25.76% <0.00%> (?)
ptq	53.05% <0.00%> (?)

[KodiaqQ]

PT nightly test build 185

185 failed due to a job options issue.
186 run was started.

[KodiaqQ]

186 run passed.