Expose erased key sentinel API + test updates #304

Job	Run time
Doxygen check	13s
Compute matrix	5s
Verify Dev Containers / Verify devcontainers	9s
CUDA11.8 gcc / amd64 / Build gcc11/C++17 / Build gcc11/C++17	3m 7s
CUDA12.3 gcc / arm64 / Build gcc12/C++17 / Build gcc12/C++17	3m 49s
CUDA12.3 gcc / amd64 / Build gcc12/C++17 / Build gcc12/C++17	3m 43s
Verify Dev Containers / List devcontainers	2s
Verify Dev Containers / cuda12.3-gcc12	53s
Verify Dev Containers / cuda12.3-gcc12	1m 0s
Verify Dev Containers / cuda11.8-gcc11	50s
CUDA11.8 gcc / amd64 / Test gcc11/C++17 / Test gcc11/C++17	5m 33s
CUDA12.3 gcc / amd64 / Test gcc12/C++17 / Test gcc12/C++17	6m 2s
CUDA12.3 gcc / arm64 / Test ${{ inputs.test_name }}	0s
CI success	1s
	25m 27s

Provide feedback