Vulkan: Implement very basic textures. This is a quick implementation which supports only one backing Image and one type of ImageView at a time, for 2D texture only. It also implements a helper class for finding compatible memory pools. It's possible we can keep a cache of memory pool indexes given the guarantees the Vulkan spec has on compatible memory types (see the documentation for VkMemoryRequirements). BUG=angleproject:2167 Change-Id: I1d7a8eaec90f240273ad75194e23430d6d4c5dc1 Reviewed-on: https://chromium-review.googlesource.com/680000 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Frank Henigman <fjhenigman@chromium.org>