Re-land "Vulkan: SwiftShader integration." Re-land fixes Win7 configs and placement of the SwiftShader module for ASAN/TSAN configs. Adds a new EGL extension for picking SwiftShader when using the Vulkan back-end. Also cleans up ICD enabling code RendererVk. Also includes a change to a buffer size necessary to support SwiftShader's minimum limits. Bug: angleproject:3876 Bug: b/140251624 Change-Id: I5e16057ac4de07bbdbbd248542b1b9103133294f Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/1810065 Commit-Queue: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org>