Vulkan: Don't assume host visibility for external buffers When importing external buffers, Vulkan ICDs could choose to import the memory into a memoryType that doesn't support the VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT property. Account for this possibility. Bug: angleproject:5073 Bug: angleproject:5909 Change-Id: Ied063b38fa48d0c8508c4aaca9214cc526f393ad Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2783669 Commit-Queue: Mohan Maiya <m.maiya@samsung.com> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Reviewed-by: Jamie Madill <jmadill@chromium.org>