Single softmax function.

[kkeroo]

This PR implements softmax util function and refactors some parsers so they use softmax from utils now.

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 50.00000% with 5 lines in your changes missing coverage. Please review.

Project coverage is 32.92%. Comparing base (37a2d92) to head (5d17383).
Report is 8 commits behind head on main.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
depthai_nodes/ml/parsers/utils/softmax.py	50.00%	2 Missing ⚠️
depthai_nodes/ml/parsers/classification.py	50.00%	1 Missing ⚠️
...epthai_nodes/ml/parsers/classification_sequence.py	50.00%	1 Missing ⚠️
depthai_nodes/ml/parsers/utils/ufld.py	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #136      +/-   ##
==========================================
- Coverage   33.40%   32.92%   -0.48%     
==========================================
  Files          68       69       +1     
  Lines        3739     3714      -25     
==========================================
- Hits         1249     1223      -26     
- Misses       2490     2491       +1     

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