Fix dialog placement

When calculating the frame for non-fullscreen windows, we incorrectly
used the wrong bounds to calculate the frame, which lead to wrong
positioning.

To fix this, we use the inset bounds, which we consider the source
of truth for all layout related aspects, to calculate the frame,
and then offset everything by the difference between the inset bounds
and the task bounds to position them correctly.

Bug: 28012565
Bug: 27860956
Bug: 27441808
Change-Id: I90d45054e0bcce78d021ad2cd20e5ef7f79ded3d