MediaVulkanGpuTest: use AIMAGE_FORMAT_PRIVATE. In the use case ImageReader does not need to enforce the color format, therefore use PRIVATE (opaque) format. Bug: 380386975 Test: atest android.graphics.cts.MediaVulkanGpuTest (cherry picked from https://android-review.googlesource.com/q/commit:bc727d3d0c56c1cf54154de10f9d9f5a1a1207d2) Merged-In: I7bbfd4a5bfa107cce1e2770f26d0e742094fa4ab Change-Id: I7bbfd4a5bfa107cce1e2770f26d0e742094fa4ab