renderdiff: script for updating golden images (#8709)

Adding a python script to enable updating new goldens into
a staging branch in the golden repo (filament-assets).

The same script can be used in github workflow to automatically
create a golden staging branch. This will be useful for users
without access to a mac (the only platform for generating
goldens as of now).

test/renderdiff/src/image_diff.py

@@ -1,3 +1,17 @@
+# Copyright (C) 2025 The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 import tifffile
 import numpy