[1/n] Fix resize for activity embedding apps

To properly handle resize, we should use the position
based on the related offset instead of the absolute bounds.

Fix: 323385114
Test: atest WMShellUnitTests:VeiledResizeTaskPositionerTest
Test: atest WMShellUnitTests:FluidResizeTaskPositionerTest
Test: Manual

Change-Id: Ie436cf6550a3d170365d9c5cf23c1adb55dfc74d