Add Ubuntu 22.04 with default g++ to GitHub Actions CI matrix

- Expand compiler testing to include Ubuntu 22.04 with default g++
- Maintain comprehensive cross-platform compiler compatibility testing
- Incrementally improve CI matrix configuration

Author: jwtowner

.github/workflows/c-cpp.yml

@@ -22,6 +22,8 @@ jobs:
             compiler: g++-12
           - os: ubuntu-24.04
             compiler: g++-13
+          - os: ubuntu-22.04
+            compiler: g++
           - os: windows-2022
             compiler: default
           - os: macos-latest