Do not start another transition from handleRequest

In DesktopModeController we were starting another transition from
handleRequest method. This lead to a stack overflow due to
dispatchRequest ending up here in handleRequest and that calling
dispatchRequest again.
Removed the dispatchRequest call here and just creating the
WindowContainerTransaction as needed.

Test: atest DesktopModeControllerTest
Bug: 274672225
Change-Id: If415fb84ffdec7a1f1cdfd8a17a368739a505f66