Rename cache flag due to gantry broken.

- rename `cache_if_source_crop_layer_only_moved` to
  `cache_when_source_crop_layer_only_moved`.
- we keep the old broken one for readability.

Bug: 305718400
Test: builds
Change-Id: I82b1275388758e7b946a310f6490e82d2bfcbd0b