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
diff --git a/vulkan/scripts/code_generator.py b/vulkan/scripts/code_generator.py
index 39fedf4..378a9c0 100755
--- a/vulkan/scripts/code_generator.py
+++ b/vulkan/scripts/code_generator.py
@@ -17,16 +17,16 @@
 # This script provides the main function for generating
 # vulkan framework directly from the vulkan registry (vk.xml).
 
-import generator_common as gencom
-import api_generator as apigen
-import driver_generator as drivergen
-import null_generator as nullgen
+import api_generator
+import driver_generator
+import generator_common
+import null_generator
 
 if __name__ == '__main__':
-  gencom.parseVulkanRegistry()
-  apigen.api_genh()
-  apigen.api_gencpp()
-  drivergen.driver_genh()
-  drivergen.driver_gencpp()
-  nullgen.null_driver_genh()
-  nullgen.null_driver_gencpp()
+  generator_common.parse_vulkan_registry()
+  api_generator.gen_h()
+  api_generator.gen_cpp()
+  driver_generator.gen_h()
+  driver_generator.gen_cpp()
+  null_generator.gen_h()
+  null_generator.gen_cpp()