Scale widgets when dragging and dropping in multi-window mode.

This change mimics the non-MW mode behavior when dragging and
dropping widgets by taking the app widget scale into consideration.
This ensures a consistant drag and drop experience between
MW mode and non-MW mode.

* Uses cell data (cell height/width, spanX/Y) to get the expected
widget sizes.
* Scales sizes when necessary.

Bug: 32176631
Change-Id: Icdaf73ecd89a30e57fe7f405292d793f2d6a3ee8