[Do Not Merge] Introduce `cast_starboard_api`. #271

Job	Run time
linux / initialize	0s
linux / docker-build-image	0s
linux / docker-unittest-image	0s
linux / ${{ matrix.name }}_${{ matrix.config }}	0s
linux / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
linux / ${{ matrix.name }}_on_device_${{ matrix.type }}	0s
	0s

Provide feedback