VK_EXT_sample_locations is not supported in SwiftShader, but all
related tests were being marked as unimplemented because
vkGetPhysicalDeviceProperties2 didn't handle
VK_STRUCTURE_TYPE_PHYSICAL_DEVICE_SAMPLE_LOCATIONS_PROPERTIES_EXT.
Explicitly ignored this case (with a proper verification that
VK_EXT_sample_locations is indeed marked as unsupported).

Bug b/117974925

Change-Id: I64a8540c0c30599c8a0a56ce322c563918ba2c31
Tests: dEQP-VK.pipeline.multisample.sample_locations_ext.*
Reviewed-on: https://swiftshader-review.googlesource.com/c/SwiftShader/+/28428Reviewed-by: Nicolas Capens <nicolascapens@google.com>
Tested-by: Alexis Hétu <sugoi@google.com>
Kokoro-Presubmit: kokoro <noreply+kokoro@google.com>