[GHA] Add Code Coverage workflow

[mkruszyx]

DO NOT MERGE - WORK IN PROGRESS

Changes

The new workflow adds coverage collection for NNCF test scopes.
Uses composite-action from openvino repository for coverage-specific steps.

Related tickets

CVS-184859

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Adds a scheduled/manual GitHub Actions workflow to run Python test suites under coverage, collect artifacts, generate an aggregated summary, and upload coverage data to Codecov.

Changes:

• Introduces a new coverage.yml workflow that runs multiple Python coverage lanes (core matrix, ExecuTorch, weight-compression split lanes) and publishes artifacts/summaries.
• Adds .github/coverage/tests_python.yml describing the Python coverage suite commands and upload metadata for the coverage toolkit.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 3 comments.

File	Description
.github/workflows/coverage.yml	New CI workflow to run coverage lanes, collect artifacts, build summary, and upload to Codecov.
.github/coverage/tests_python.yml	New Python coverage suite definition (commands, artifacts, uploads) consumed by the coverage toolkit action.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 90.81%. Comparing base (3695da7) to head (da9dc44).
⚠️ Report is 880 commits behind head on develop.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #4071      +/-   ##
===========================================
- Coverage    91.29%   90.81%   -0.49%     
===========================================
  Files          496      299     -197     
  Lines        47676    29377   -18299     
===========================================
- Hits         43526    26678   -16848     
+ Misses        4150     2699    -1451     

see 795 files with indirect coverage changes

Flag	Coverage Δ
COMMON	?
ONNX	?
OPENVINO	?
TENSORFLOW	?
TORCH	?
nncf-python-common	27.40% <ø> (?)
nncf-python-executorch	41.76% <ø> (?)
nncf-python-gptqmodel_cuda	26.10% <ø> (?)
nncf-python-onnx	50.55% <ø> (?)
nncf-python-openvino	56.13% <ø> (?)
nncf-python-tools	0.00% <ø> (?)
nncf-python-torch_cpu	61.12% <ø> (?)
nncf-python-torch_cuda	51.85% <ø> (?)
nncf-python-wc_1	39.38% <ø> (?)
nncf-python-wc_2	43.60% <ø> (?)
nncf-python-wc_3	41.71% <ø> (?)
nncf-python-wc_4	42.15% <ø> (?)
nncf-python-wc_5	40.56% <ø> (?)
nncf-python-wc_6	45.04% <ø> (?)

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

Components	Coverage Δ
common	∅ <ø> (∅)
torch	∅ <ø> (∅)
tensorflow	∅ <ø> (∅)
onnx	∅ <ø> (∅)
openvino	∅ <ø> (∅)
ptq	∅ <ø> (∅)

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[AlexanderDokuchaev]

Questions in JIRA was ignored, so close PR