Flag to not allow split task to have bounds set

Tasks in split screen should inherit bounds from the split root tasks.
If task had bounds set in a different multitasking mode, when it enters
split screen, these bounds should be cleared.
Create a flag to enable this behavior.

Bug: 427245857
Flag: EXEMPT, adding flag
Test: presubmit
Change-Id: If2f1e7581f2c88eb336b8be5979d3b30269429e9