This extension allows one to import/export device memory buffers
through shared memory region file descriptors.

This also adds checks to ensure that binding a buffer or image
to an external device memory works only if VkCreate{Buffer,Image}
was called with a VkExternalMemory{Buffer,Image}CreateInfo struct
with compatible handle types.

Test: dEQP-VK.api.external.memory.opaque_fd*

Bug: b/140419396
Change-Id: I5d249685896ae0764bc9d5c635cc3799323db453
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/35152
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: David Turner <digit@google.com>