Added functions to return properties for external objects.
All properties are currently disabled.

Bug b/117974925

Change-Id: I3322ab7125bddef41f50b0160c22687a1182ae16
Tests: dEQP-VK.api.external.*
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28770Tested-by: Alexis Hétu <sugoi@google.com>
Presubmit-Ready: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>
Reviewed-by: Chris Forbes <chrisforbes@google.com>
Reviewed-by: Nicolas Capens <nicolascapens@google.com>