[CodeGen][Unit Test] Add unit test to flag vk.py discrepancies from vk.xml changes

Key Changes:
* Unit Test Case for flagging outdated vk.py (from vk.xml)
* Updated gen_vk() in vk_parser to pass the xml_root for vk.xml
* Added fix for resolving path to vk.xml

Bug: 410759458
Test: N/A
Flag: NONE infeasible
Change-Id: Ida7d5de43f9d433193c6d58e478a5cf0c40fcd22