Vulkan: Extend coherent adv blend to emulated path * blendEquationAdvancedCoherentKHR is now also enabled if the following features are enabled to emulate ABE: * emulateAdvancedBlendEquations * supportsShaderFramebufferFetch * Relevant tests: *GLES31.functional.blend_equation_advanced.coherent* * On some Android devices: From "Not supported" to "Passed" Bug: angleproject:42262258 Change-Id: I4d97438df774f0752b9f30c5807cb3cc20ede076 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/5631144 Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Amirali Abdolrashidi <abdolrashidi@google.com> Reviewed-by: Cody Northrop <cnorthrop@google.com>