Fix: Update deprecated actions and resolve subsequent build failures

- Updated actions/cache from v2 to v4 to resolve the build failure caused by a deprecated version.
- Updated actions/checkout from v2 to v4 as a proactive measure.

These changes revealed further build failures, which are also fixed in this PR:

1.  The `clang-13` package is not available on `ubuntu-latest` runners. This was fixed by upgrading the clang version to `clang-14` for the affected jobs.
2.  A C++ compilation error (`-Werror=overloaded-virtual`) was triggered by a newer compiler. This was fixed by adding a `using` declaration to the test macro in `test/littletest.hpp`.
3. The `valgrind-dbg` package is not available on `ubuntu-latest`. This was fixed by removing it from the installation step.

Author: google-labs-jules[bot]

.github/workflows/verify-build.yml

@@ -294,7 +294,7 @@ jobs:
       if: ${{ matrix.compiler-family == 'gcc' && matrix.os-type == 'ubuntu' }}
 
     - name: Install valgrind if needed
-      run: sudo apt-get install valgrind valgrind-dbg
+      run: sudo apt-get install valgrind
       if: ${{ matrix.build-type == 'valgrind' && matrix.os-type == 'ubuntu' }}
 
     - name: Install cpplint if needed