Vulkan: Add support for EXT_shader_framebuffer_fetch_non_coherent EXT_shader_framebuffer_fetch_non_coherent is implemented using subpass input attachments. The extension will be enabled in a follow up change that adds required changes to the Vulkan translator. Bug: angleproject:5454 Test: FramebufferFetchNonCoherentES31.*Vulkan Change-Id: Ic73c66a476c4a21db5269431166a198841f1dc0c Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2598059 Commit-Queue: Mohan Maiya <m.maiya@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>