vulkan: clean up the framework generation script

1. Instead of mixing up all code formats, stick to pep8 and python style guide
2. Removed some redundant functions
3. Simplified seme code logic
4. Move constant codes back to main code gen blocks for readibility
5. Moved most of the hard-coded constants to the top
6. Removed a redundant clang format hint
7. Removed any mention of the legacy code gen stuff

Bug: 134185757
Test: ./scripts/code_generator.py && build
Change-Id: I1eca91fb0d181b7e8353c4c6a651d80ed1f2d1e0