[CodeGen] Add guides for Vulkan pipeline updates and presubmit failures

** vulkan/README.md`: Updates the existing README with a detailed guide
on how to update the Vulkan device info pipeline.

** vulkan/scripts/test/README.md: Provides instructions on how to fix
`vk.py` sync failures that occur during presubmit tests.

Bug: 435352424
Test: NONE
Flag: NONE infeasible
Change-Id: I4ea7d60ebb38e4637bcc803535ca9b6c4ef197a0