Fixed cts failure of WindowInsetsControllerTests

If the device is a tablet, the navigation bar will be taskbar, and it
will draw fake rounded corners above itself when it's shown and
unstashed. When apps request to hide taskbar from such state, it will
cause an extra window insets change from server side.

Move the calculation of rounded corner inset to client side so that we
can make the window insets change come only once.

Bug: 229825307
Test: atest WindowInsetsControllerTests ActivityRecordTests
Change-Id: I081142facbe0fe676b89c8883fa690ba5ae13d79