Resize PiP proportionally upon fold/unfold

Make sure to resize pip proportionally upon folding
or unfolding while keeping it withing the allowed
bounds provided by the pip size spec.

Bug: 302205188
Bug: 302394468
Bug: 301414095
Test: repro the steps in the bug
Test: atest WMShellUnitTests:PipBoundsStateTest
Change-Id: I9eb0b45c84f847dca40b71d4747b9a7ac9711c43