Remove width from the edge when MAX_PARALLAX exceeded

If max_parallax is exceeded by a legacy wallpaper, the user will
experience a shift of the wallpaper after enabling multi_crop if we
remove width from both sides, as per b/345127272.

Adjust the tests accordingly.

Flag: ACONFIG com.android.window.flags.multi_crop TRUNKFOOD
Bug: 345127272
Test: atest WallpaperCropperTest
Change-Id: Ie3160db05c5bf66c50ad9f70f33787abe675f36d