Speed up CI builds

[daredoole]

Summary

• switch Ubuntu and sanitizer builds to Ninja with ccache restore/save
• make Fedora RPM validation run package tests in %check
• remove the duplicate Fedora standalone CMake build/test after the RPM build
• allow CI to pass optional RPM CMake args without making ccache a packaging dependency

Validation

• bash -n scripts/validate-rpm-packaging.sh
• scripts/validate-rpm-packaging.sh
• cmake -S . -B build-ninja -G Ninja -DCMAKE_BUILD_TYPE=Release
• cmake --build build-ninja --parallel 2
• ctest --test-dir build-ninja --output-on-failure
• MWB_VALIDATE_RPM_BUILD=1 MWB_RPM_CMAKE_EXTRA_ARGS="-G Ninja" scripts/validate-rpm-packaging.sh
• git diff --check