1. Enable glColorspace if VK_EXT_swapchain_colorspace is
supported, remove dependency on VK_KHR_image_format_list.
2. Enable VK_KHR_image_format_list support on Mali GPU.
3. Fix PbufferTest.ClearAndBindTexImageSrgbSkipDecode
   test tolerance issue.

Bug: angleproject:2514
Bug: angleproject:5281
Change-Id: I2ed54a14afc7c3aee5a5980bd300ab052ebab3d1
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2793852
Commit-Queue: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>