renderdiff: add golden repo support (#8689)

- Add GoldenManager to manage access to the repo containing the
  goldens
- Add tif comparison code
- Enable comparison by default for actual test

test/renderdiff/src/image_diff.py

@@ -0,0 +1,29 @@
+import tifffile
+import numpy
+
+def same_image(tiff_file_a, tiff_file_b):
+  try:
+    img1_data = tifffile.imread(tiff_file_a)
+    img2_data = tifffile.imread(tiff_file_b)
+
+    # If the dimensions (height, width, number of channels, number of pages/frames)
+    # are different, the images are not the same.
+    if img1_data.shape != img2_data.shape:
+      print(f"Images have different shapes: {img1_data.shape} vs {img2_data.shape}")
+      return False
+
+    # numpy.array_equal() checks if two arrays have the same shape and elements.
+    if numpy.array_equal(img1_data, img2_data):
+      return True
+    else:
+      return False
+
+  except FileNotFoundError:
+    print(f"Error: One or both files not found ('{file_path1}', '{file_path2}').")
+    return False
+  except tifffile.TiffFileError as e:
+    print(f"Error: One or both files are not valid TIFF files or could not be read. Details: {e}")
+    return False
+  except Exception as e:
+    print(f"An unexpected error occurred: {e}")
+    return False