RESTRICT AUTOMERGE MRImageReader Impl of ResultDispatcher

Enable camera HAL to return any one stream within the same stream group
of the request streams for MultiResolution ImageReader.

Bug: 213420874
Test: build pass, basic functionality tests
Test: atest CtsCameraTestCases:MultiResolutionImageReaderTest
Test: MR test apk
Test: go/pixel-camera-test-checklist
Change-Id: Ie64a384d66ad1441f91107d4e65cc33677769133