vulkan: Update vulkan headers to 1.0.38

Catches up with the current upstream header. Preserves the local changes
for incremental present.

V2: Fix indentation issues
V3: Add missing struct and defines for EXT_validation_flags

Change-Id: I6e4f44e0eba8de00b010a6918ec2ba92614cc6bc
Test: Ensured cube demo still works