Add early stopping with warmup. Remove mandatory background label in semantic segmentation task

[kprokofi]

Summary

Motivation:

1. Early stopping from lightning doesn't have a warmup parameter and it leads to underfitting when training on small Geti target datasets. I added two thresholds to have invariant for small datasets that can fit in one batch and for larger data

2. Inserting a background label actually can lead to class mismatches for the Segmentation head, sometimes datasets don't have background classes at all. I tried to divide the Geti case with polygons and ordinary training from file masks. When dm_dataset represents annotations with Polygons -> we insert a background label and create a head with num_classes + 1. For other cases, dataset_meta.json should explicitly reflect all classes for training. So, the number of indices in masks == num categories in dataset_meta.json.
   Before these changes, if we add a background class to dataset_meta.json, the training will fail, because OTX deletes the background class during prefiltering. Now, the background class must be presented in a metadata file when needed.

How to test

Checklist

• I have added unit tests to cover my changes.​
• I have added integration tests to cover my changes.​
• I have ran e2e tests and there is no issues.
• I have added the description of my changes into CHANGELOG in my target branch (e.g., CHANGELOG in develop).​
• I have updated the documentation in my target branch accordingly (e.g., documentation in develop).
• I have linked related issues.

License

• I submit my code changes under the same Apache License that covers the project.
  Feel free to contact the maintainers if that's a concern.
• I have updated the license header for each file (see an example below).

# Copyright (C) 2024 Intel Corporation
# SPDX-License-Identifier: Apache-2.0

[codecov]

Codecov Report

Attention: Patch coverage is 65.38462% with 9 lines in your changes are missing coverage. Please review.

Project coverage is 82.86%. Comparing base (ce2d99f) to head (3beac1b).
Report is 3 commits behind head on develop.

Files	Patch %	Lines
src/otx/core/data/dataset/segmentation.py	55.55%	4 Missing ⚠️
src/otx/algo/callbacks/adaptive_early_stopping.py	81.81%	2 Missing ⚠️
src/otx/core/data/pre_filtering.py	33.33%	2 Missing ⚠️
src/otx/core/types/label.py	66.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #3515      +/-   ##
===========================================
- Coverage    82.99%   82.86%   -0.14%     
===========================================
  Files          253      254       +1     
  Lines        25163    24945     -218     
===========================================
- Hits         20885    20670     -215     
+ Misses        4278     4275       -3     

Flag	Coverage Δ
py310	82.24% <65.38%> (-0.27%)	⬇️
py311	82.74% <65.38%> (-0.23%)	⬇️

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[harimkang]

LGTM