ci: oneshot-test: include matrix index in the name of failed-test artifact

Add a matrix index to the name of failed-test artifact, in order
to be able to distinguish between artifacts produced for same OS
and python version, but with different requirements list.

Author: rokm

.github/workflows/oneshot-test.yml

@@ -220,5 +220,5 @@ jobs:
         if: ${{ failure() && steps.run-tests.outcome == 'failure' }}
         uses: actions/upload-artifact@v6
         with:
-          name: failed-tests-${{ matrix.os }}-python-${{ matrix.python-version }}
+          name: failed-tests-${{ matrix.os }}-python-${{ matrix.python-version }}-matrix-idx-${{ strategy.job-index }}
           path: '${{ env.PYTEST_DEBUG_TEMPROOT }}/archived-failed-tests.tar'