devel/pyside2: add more qt5 dependencies

Qt5RemoteObjects is an "optional" module for pyside2 - it will be picked
up automatically when qt5-remoteobjects is found during pyside2's build.
Add it to enable the full functionality of pyside2, and to avoid staging
errors in unclean environments. [1]
The Qt53DExtras module may pull in qt5-gamepad (another contaminated-
build-issue is suspected), depend on qt5-gamepad to avoid breakage in
case this had happened with qt53DExtras. [1]
While here, remove some now-obsolete staging area cleanup, the files are
not installed anymore by the port. [2]

PR: 241855
Reported by: rhurlin@gwdg.de [1]