Python: Add PR number to test coverage workflow (#9964)

### Motivation and Context

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The test coverage workflow needs the PR number to post comments to PRs.
However, the `workflow_run` context doesn't contain the PR number thus
we need to save it.

### Description

<!-- Describe your changes, the overall approach, the underlying design.
These notes will help understanding how your code works. Thanks! -->
Save the PR number in a file and upload it as artifact for the second
workflow to use.

### Contribution Checklist

<!-- Before submitting this PR, please make sure: -->

- [x] The code builds clean without any errors or warnings
- [x] The PR follows the [SK Contribution
Guidelines](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md)
and the [pre-submission formatting
script](https://github.com/microsoft/semantic-kernel/blob/main/CONTRIBUTING.md#development-scripts)
raises no violations
- [x] All unit tests pass, and I have added new tests where possible
- [x] I didn't break anyone 😄

.github/workflows/python-test-coverage-report.yml

@@ -25,10 +25,19 @@ jobs:
           merge-multiple: true
       - name: Display structure of downloaded files
         run: ls
+      - name: Read and set PR number
+        # Need to read the PR number from the file saved in the previous workflow
+        # because the workflow_run event does not have access to the PR number
+        # The PR number is needed to post the comment on the PR
+        run: |
+          PR_NUMBER=$(cat pr_number)
+          echo "PR number: $PR_NUMBER"
+          echo "::set-env name=PR_NUMBER::$PR_NUMBER"
       - name: Pytest coverage comment
         id: coverageComment
         uses: MishaKav/pytest-coverage-comment@main
         with:
+          issue-number: ${{ env.PR_NUMBER }}
           pytest-coverage-path: python/python-coverage.txt
           title: "Python Test Coverage Report"
           badge-title: "Python Test Coverage"

.github/workflows/python-test-coverage.yml

@@ -21,6 +21,11 @@ jobs:
       UV_PYTHON: "3.10"
     steps:
       - uses: actions/checkout@v4
+      # Save the PR number to a file since the workflow_run event
+      # in the coverage report workflow does not have access to it
+      - name: Save PR number
+        run: |
+          echo ${{ github.event.number }} > ./pr_number
       - name: Set up uv
         uses: astral-sh/setup-uv@v4
         with:
@@ -37,6 +42,7 @@ jobs:
           path: |
             python/python-coverage.txt
             python/pytest.xml
+            python/pr_number
           overwrite: true
           retention-days: 1
           if-no-files-found: error