HaikuDepot: Only send package status change notifications...

...if the package status actually did change.
HaikuDepot: Miscellanous improvements to package state tracking.

- MainWindow now listens for package installation state changes so
  it can keep Model's package location lists in sync.
- PackageListView now updates its status column on package state changes.
- PackageInfoView now updates the available action list when package
  installation state changes.
- PackageManager populates the expected user-specified install/uninstall
  package sets for ProblemWindow so that one can properly filter those out.

There still remain some issues with the installed locations for ResultWindow
not being entirely correct though, which causes issues for package
uninstallation.