[ScreenDecor CLI] ScreenDecorCommand based on ParseableCommand

This CL implements the ScreenDecorCommand class based on the new
ParseableCommand definitions. This approach lets us move all of the
parsing into the lib and handle the command object in a cleaner way.

Test: manual
Bug: 285941724
Change-Id: Ic801c654ade599dc4921994836ead46c2bba9f69