Add simple `MediaSourceAttachment` class #12422

Job	Run time
android-arm64 / initialize	43s
android-arm / initialize	43s
android-x86 / initialize	44s
android-arm / docker-build-image	1m 29s
android-arm / docker-unittest-image	0s
android-arm64 / docker-build-image	1m 25s
android-arm64 / docker-unittest-image	0s
android-x86 / docker-build-image	1m 29s
android-x86 / docker-unittest-image	0s
android-arm64 / arm64_devel	17m 50s
android-arm64 / arm64_debug	20m 21s
android-arm64 / arm64_qa	8m 17s
android-arm64 / arm64_gold	7m 43s
android-arm / arm_devel	17m 47s
android-arm / arm_debug	17m 13s
android-arm / arm_qa	7m 55s
android-arm / arm_gold	8m 4s
android-x86 / x86_devel	16m 37s
android-x86 / x86_debug	19m 10s
android-x86 / x86_qa	7m 53s
android-x86 / x86_gold	8m 3s
android-arm / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
android-arm / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
android-x86 / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
android-x86 / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
android-arm64 / ${{ matrix.name }}_${{ matrix.shard }}_test	0s
android-arm64 / ${{ matrix.name }}_on_device_${{ matrix.shard }}	0s
upload-release-artifacts	25s
	2h 43m 51s

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