Vulkan: Force flush staged updates for external textures For textures that are backed by external memory, immediately flush sub image updates instead of staging them. Bug: angleproject:4828 Tests: angle_end2end_tests --gtest_filter=ImageTest.UpdatedExternalTexture* Change-Id: I51e5bd0cb5df7df3af21f0cdb3007eebc1be29cd Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2290490 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org> Commit-Queue: Mohan Maiya <m.maiya@samsung.com>