ci: improve CI stability with parallel builds and Valgrind

Major changes:
Run 4 build configurations in parallel with Valgrind on Linux
Add test failure detection verification (meta-test)
Port allocation per build to prevent conflicts in parallel runs
Add --coverage-only flag for dedicated coverage builds
Code quality:

Add TEST_GROUPS constant, CMOCKA patterns, helper functions
Organize ci-build.sh into sections

.github/workflows/ci-code.yml

@@ -106,20 +106,5 @@ jobs:
       - uses: actions/checkout@v4
       - name: Build and run coverage
         run: |
-          docker build -f Dockerfile.debian -t profanity-cov .
-          docker run -v ${{ github.workspace }}/coverage:/coverage profanity-cov bash -c '
-            ./bootstrap.sh
-            ./configure --enable-coverage --enable-otr --enable-pgp --enable-omemo --enable-plugins
-            make -j$(nproc)
-            make check || true
-            make check-functional-parallel || true
-            lcov --capture --directory . --output-file /coverage/coverage.info \
-              --rc branch_coverage=1 \
-              --ignore-errors inconsistent
-            lcov --remove /coverage/coverage.info \
-              "/usr/include/*" "*/tests/*" \
-              --output-file /coverage/coverage.info \
-              --rc branch_coverage=1 \
-              --ignore-errors inconsistent,empty,unused
-            lcov --summary /coverage/coverage.info
-          '
+          docker build -f Dockerfile.arch -t profanity-cov .
+          docker run profanity-cov ./ci-build.sh --coverage-only