vulkan: refactor order-only header gen deps
What does this MR do and why?
vulkan: refactor order-only header gen deps
Summary:
- commit 1 (dropped since landed separately): !28062 (merged), which is to fix a recent regression in vulkan runtime internal libraries' use of headers generated out-of-order
- commit 2 and 3: cleanup and ensure robust wsi_entrypoints gen order
- commit 4 and 5: cleanup and ensure robust runtime headers gen order