Screen capture: Region box tap target sizes for mouse vs touch

A mouse is a much more precise tool than using a touch-based device. As
such, the region box tap targets should be smaller for a mouse and
larger for touch.

Also refactors a few internal methods of RegionBoxState to return a
resize zone based on the current pointer type and its respective tap
target size.

Bug: 435503791
Test: atest RegionBoxStateTest
Flag: com.android.systemui.large_screen_screencapture
Change-Id: Iaa31c48e4d376eb4de96af0544295f25e15b0777