Several BlendIntegerTest tests are failing due to an update to the
Vulkan Validation Layers that are now checking if formats support
VK_FORMAT_FEATURE_COLOR_ATTACHMENT_BLEND_BIT and generating an error
if not while pipeline.pColorBlendState.pAttachments[0].blendEnable
is VK_TRUE.

Bug: angleproject:4571
Test: BlendIntegerTest*
Change-Id: Ibbfe415af3d6d6a879a502adb6541a5bfe8cd13a
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2152947Reviewed-by: Courtney Goeltzenleuchter <courtneygo@google.com>
Commit-Queue: Tim Van Patten <timvp@google.com>