Add test for getBubbleBarExpandedViewBounds

Adds unit test for getBubbleBarExpandedViewBounds introduced in
ag/26520235.

Also fixes a bug with positioning the expanded view on the right if
device has insets on the left and right.
Previously we were using the width of available area when determining
left position for the expanded view. But width of the available area
includes left and right insets. For positioning we should only be
looking at the insets for the side where the bubble expanded view is.

Bug: 313661121
Test: atest WMShellMultivalentTestsOnDevice:BubblePositionerTest
Test: atest WMShellRobolectricTests:BubblePositionerTest
Change-Id: Ib6fa5c427404cbbe36737427e3bfcf432a0d5d6a