Add tests for RGB8 and RGBA8 renderbuffer usage * Added simple tests for RGB8 and RGBA8 renderbuffer usage for GLES1 and GLES2+. Bug: angleproject:352352894 Change-Id: Ie410c57ab204c2afad3f53c37578865bd9e9307f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/6050343 Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Auto-Submit: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>