Newer Vulkan CTS has started providing this extension structure during
device creation.

Bug: b/139528538
Change-Id: Ied17274d95acb8be1766f62e21fcc1c6b7594015
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35249Tested-by: Chris Forbes <chrisforbes@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>