Add focusability into the hierarchy and Container transaction

Split-screen will eventually be replaced by a hierarchical
mechinasm. This means the RAC.mIsDockMinimized and primary split
checking will go away.

In its place, add focusable to windowcontainer and have it
override all children's focusability.

Also, fixes a bug where activity configuration wasn't updated
properly after a WC transaction.

Bug: 133381284
Test: added wmtest
Change-Id: I35ed1561cc32785528854a8a53e52a13144f31c1