Add SystemApi to set unrestricted keep-clear rects

This CL allows applications to choose whether to set restricted or
unrestricted keep-clear areas by adding a dedicated SystemApi for
unrestricted keep-clear areas - View#setUnrestrictedKeepClearRects. The
SET_UNRESTRICTED_PREFER_KEEP_CLEAR_AREAS permission is now only checked
for keep-clear areas from that API

Bug: 221094507
Test: atest CtsWindowManagerDeviceTestCases:KeepClearRectsTests
Test: atest WindowStateTests#testUnrestrictedKeepClearAreas
Change-Id: I89ca3149117b4d457c5521d617880870706d7793