Add markdown test summaries and a coverage HTML report to CI

ctest_summary.py renders a Test.xml as markdown for
GITHUB_STEP_SUMMARY: a one-liner when everything passes, otherwise the
first few failures inline with a link to the full Test.xml on MinIO.
It's also usable locally with --all to list every failure from a
downloaded Test.xml.

The coverage job now also generates and uploads gcovr's html-details
report and links it from the step summary.

.gitea/workflows/ci.yml

@@ -112,6 +112,13 @@ jobs:
           zstd build/Testing/*/Test.xml
           mc cp build/Testing/*/Test.xml.zst "minio/jenkins/conflict-set/${{ gitea.run_number }}/${{ matrix.name }}/"
 
+      - name: Test summary
+        if: always()
+        run: |
+          python3 ctest_summary.py build/Testing/*/Test.xml \
+            --link "https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/${{ matrix.name }}/Test.xml.zst" \
+            >> "$GITHUB_STEP_SUMMARY"
+
   release:
     needs: build-image
     strategy:
@@ -193,6 +200,13 @@ jobs:
             mc cp paper/*.pdf "$dest"
           fi
 
+      - name: Test summary
+        if: always()
+        run: |
+          python3 ctest_summary.py build/Testing/*/Test.xml \
+            --link "https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/release-${{ matrix.arch }}/Test.xml.zst" \
+            >> "$GITHUB_STEP_SUMMARY"
+
   coverage:
     needs: build-image
     runs-on: ubuntu-latest-amd64
@@ -232,6 +246,8 @@ jobs:
                      --gcov-executable "llvm-cov gcov" --exclude-noncode-lines)
           gcovr "${gcov_args[@]}" --cobertura > build/coverage.xml
           gcovr "${gcov_args[@]}"
+          mkdir -p build/coverage_html
+          gcovr "${gcov_args[@]}" --html-details build/coverage_html/index.html
           gcovr "${gcov_args[@]}" --fail-under-line 100 > /dev/null
 
       - name: Upload results to MinIO
@@ -250,3 +266,15 @@ jobs:
           if [ -e build/coverage.xml ]; then
             mc cp build/coverage.xml "$dest"
           fi
+          if [ -d build/coverage_html ]; then
+            mc cp -r build/coverage_html "$dest"
+          fi
+
+      - name: Test summary
+        if: always()
+        run: |
+          python3 ctest_summary.py build/Testing/*/Test.xml \
+            --link "https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/coverage/Test.xml.zst" \
+            >> "$GITHUB_STEP_SUMMARY"
+          echo "" >> "$GITHUB_STEP_SUMMARY"
+          echo "📊 [Coverage report](https://minio.weaselab.dev/jenkins/conflict-set/${{ gitea.run_number }}/coverage/coverage_html/index.html)" >> "$GITHUB_STEP_SUMMARY"