Combine clipping rect iOS scenario test goldens to reduce maintenance burden keeping them updated

The iOS scenario screenshots are a maintenance burden ([see their update instruction](https://github.com/flutter/engine/tree/main/testing/scenario_app/ios/Scenarios/ScenariosUITests)) to keep updated, and are checked into the engine repo. I'm hitting this pain now turning on [more tests for impeller](https://github.com/flutter/flutter/issues/131888), but they also have to be updated every time we do a major iOS update.

https://github.com/flutter/engine/pull/54820 created 12 new clipping test golden screenshots. Can the new multiclip goldens be removed, and instead added as a new shape to the existing clip screenshots? For example, the new shape is right under the old shape? For example, [this screenshot](https://github.com/flutter/engine/blob/main/testing/scenario_app/ios/Scenarios/ScenariosUITests/golden_two_platform_view_clip_path_iPhone%20SE%20(3rd%20generation)_17.0_simulator.png) is testing multiple images at the same time:

cc @hellohuanlin