Cleanup local build.py to utilize central scripts

Centralize the copying actions so we can better deal with the build edge cases in one spot.

build.py

 #!/usr/bin/python -B
 import os
-import json
-import shutil
-import textwrap
-
-sub_packages = {}
-sub_package_folders = {}
-publish_order = []
 
 def packages_list():
     return [
-# helper function for preparations of tests
-def copy_path_to_project(path, repo_path, project_path, logger):
-    logger.info("Copying {}".format(path))
-    shutil.copytree(os.path.join(repo_path, path), os.path.join(project_path, "Assets", os.path.basename(path)))
-
-def copy_file_to_project(path, repo_path, project_path, logger):
-    logger.info("Copying {}".format(path))
-    shutil.copy(os.path.join(repo_path, path), os.path.join(project_path, "Assets", path))
-
-    copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "NewNodes"), repo_path, project_path, logger)
-    copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "TestAssets"), repo_path, project_path, logger)
-    copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "UnityShaderEditor", "Editor", "Testing"), repo_path, project_path, logger)
+    import unity_package_build
+    unity_package_build.copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "NewNodes"), repo_path, project_path, logger)
+    unity_package_build.copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "TestAssets"), repo_path, project_path, logger)
+    unity_package_build.copy_path_to_project(os.path.join("MaterialGraphProject", "Assets", "UnityShaderEditor", "Editor", "Testing"), repo_path, project_path, logger)
 
 if __name__ == "__main__":
     import sys