Removing the Worskapce as a dependency of CellLayout

This will make it easier to test CellLayout, also we should avoid
circular dependencies as much as poisble.

This also allows the CellLayout to be created in other containers
that are not workspace.

Bug: 318417510
Test: creating HotseatReorderUnitTest in follow up cl
Test: TaplReorderWidgets
Test: ReorderAlgorithmUnitTest
Flag: NA
Change-Id: Ic45029a244cb11f8d6775c50b90af9c56f01eaa3