Remove test mode from VirtualCameraRenderThread.

Instead of rendering the input in the render thread of virtual camera
connect the test client with dedicated thread for input rendering
when creating a test camera.

Rendering input in test mode was slowing down the virtual camera render
thread, causing it to fail tests requiring high fps on some targets.

This cl also moves test pattern rendering to be done on GPU and cleans
up corresponding shader.

Bug: 338251124
Test: atest virtual_camera_tests
Test: manual with OpenCamera
Test: atest CtsVirtualDevicesCameraCtsTestCases
Change-Id: I4bcefd91701f2f9e195eb71c0189efbb674e58f8