From VK_EXT_external_memory_host, there is a type of VkDeviceMemory
that takes a pointer to host mapped foreign memory, where the
underlying memory is owned by the host, not the device.
This is used by ANGLE on Mac when creating a VkDeviceMemory given an
IOSurface.

Tests: dEQP-VK.*
Bug: chromium:1965434
Change-Id: I944a5d3cd23ad8b193f58981829a8847419a4b0d
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/39968
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Alexis Hétu <sugoi@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Jonah Ryan-Davis <jonahr@google.com>