scripts: Add wrapper script for all codegen

Simplify running the 3 different code generators with a wrapper script.
Provides options:
    --verify         diff generator output and repo files
    --incremental    only touh files that actually changed

Add wrapper script to CMake as VulkanVL_generated_source target

Change-Id: I9d8440092748adf546602bd1f1b204470cf161aa
diff --git a/scripts/lvl_genvk.py b/scripts/lvl_genvk.py
index cd9612e..b35b3a9 100644
--- a/scripts/lvl_genvk.py
+++ b/scripts/lvl_genvk.py
@@ -651,6 +651,10 @@
 
     args = parser.parse_args()
 
+    # default scripts path to be same as registry
+    if not args.scripts:
+        args.scripts = os.path.dirname(args.registry)
+
     scripts_directory_path = os.path.dirname(os.path.abspath(__file__))
     registry_headers_path = os.path.join(scripts_directory_path, args.scripts)
     sys.path.insert(0, registry_headers_path)