[ScreenCaptureTest] Remove captureDisplay.

Replace usages of ScreenCapture#captureDisplay with
ScreenCapture#captureLayers. Clean up repetitive
variables and setup that is already performed in
LayerTransactionTest. Move
Surface_test#ScreenshotsOfProtectedBuffersDontSucceed
to where other screenshot tests are and clean up its
logic.

Bug: 293445881
Bug: 303673371
Test: atest ScreenCaptureTest
Test: atest SurfaceTest
Test: atest LayerTransactionTest
Change-Id: Iba7e0f9e3f1b97bf503b3007112850b25867aa86