VK_KHR_spirv_1_4 is trivial because vtn already supports all the added
SPIR-V features that aren't gated behind Vulkan extensions. I've
observed some robustness2 CTS tests requiring this. However there are
a few tests currently failing due to lacking spilling.

VK_EXT_scalar_block_layout should also be trivial, since support for
"straddling" UBO loads was added recently for other reasons. This is
used by every robustness2 CTS test.

Part-of: <mesa/mesa!8695>