Add supplement GL_ARM_shader_framebuffer_fetch_depth_stencil tests * Add two tests about detaching the depth attachment and stencil attachment separately works correctly. * Add six tests to test whether multisample, GL_FETCH_PER_SAMPLE_ARM and fragment discard work properly in different situations. Bug: angleproject:385170273 Change-Id: I8a4299e2336a8bf800ffe286775a53f59b407c8e Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6108524 Reviewed-by: Charlie Lao <cclao@google.com> Commit-Queue: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>