Create and upload junit-xml artifacts (#617)

With this PR we start storing junit-xml output from test runs, in order to allow tools to be used to display and query test data. Given appropriate tools, this should have some advantages, e.g.
- understanding patterns of flakiness in tests across matrix builds within a run, and across runs
- easier understanding of how one particular build has failed

Author: dandavison

.github/workflows/ci.yml

@@ -59,17 +59,25 @@ jobs:
       - run: poetry install --no-root --all-extras
       - run: poe lint
       - run: poe build-develop
-      - run: poe test -s -o log_cli_level=DEBUG
+      - run: mkdir junit-xml
+      - run: poe test -s -o log_cli_level=DEBUG --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}.xml
       # Time skipping doesn't yet support ARM
       - if: ${{ !endsWith(matrix.os, '-arm') }}
-        run: poe test -s -o log_cli_level=DEBUG --workflow-environment time-skipping
+        run: poe test -s -o log_cli_level=DEBUG --workflow-environment time-skipping --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--time-skipping.xml
       # Check cloud if proper target and not on fork
       - if: ${{ matrix.cloudTestTarget && (github.event.pull_request.head.repo.full_name == '' || github.event.pull_request.head.repo.full_name == 'temporalio/sdk-python') }}
-        run: poe test -s -o log_cli_level=DEBUG -k test_cloud_client
+        run: poe test -s -o log_cli_level=DEBUG -k test_cloud_client --junit-xml=junit-xml/${{ matrix.python }}--${{ matrix.os }}--cloud.xml
         env:
           TEMPORAL_CLIENT_CLOUD_API_KEY: ${{ secrets.TEMPORAL_CLIENT_CLOUD_API_KEY }}
           TEMPORAL_CLIENT_CLOUD_API_VERSION: 2024-05-13-00
           TEMPORAL_CLIENT_CLOUD_NAMESPACE: sdk-ci.a2dd6
+      - name: "Upload junit-xml artifacts"
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: junit-xml--${{github.run_id}}--${{github.run_attempt}}--${{ matrix.python }}--${{ matrix.os }}
+          path: junit-xml
+          retention-days: 14
 
       # Confirm protos are already generated properly with older protobuf
       # library and run test with that older version. We must downgrade protobuf