Remove usage of events for the core

[dalyIsaac]

Relying on events for internal state changes leads to bad interleaving and out-of-order updates (#93).

Remove the following subscriptions:

src\Whim\Monitor\MonitorManager.cs:
61  	public void Initialize()
62  	{
63  		// Listen for changes in the monitors.
64: 		SystemEvents.DisplaySettingsChanging += SystemEvents_DisplaySettingsChanging;
65: 		_configContext.WindowManager.WindowFocused += WindowManager_WindowFocused;
66  	}
67
68  	private void WindowManager_WindowFocused(object? sender, WindowEventArgs e)

src\Whim\Monitor\Screen.cs:
164  						//sync the UserPreference.Desktop change event.  We'll keep count
165  						//of desktop changes so that the WorkingArea property on Screen
166  						//instances know when to invalidate their cache.
167: 						SystemEvents.UserPreferenceChanged += new UserPreferenceChangedEventHandler(OnUserPreferenceChanged);
168
169  						s_desktopChangedCount = 0;
170  					}

src\Whim\Workspace\Workspace.cs:
118  		}
119
120  		// Subscribe to window focus events
121: 		_configContext.WindowManager.WindowFocused += WindowManager_WindowFocused;
122  	}
123
124  	private void WindowManager_WindowFocused(object? sender, WindowEventArgs e)

src\Whim\Workspace\WorkspaceManager.cs:
76  		}
77
78  		// Subscribe to <see cref="IWindowManager"/> events.
79: 		_configContext.WindowManager.WindowRegistered += WindowManager_WindowRegistered;
80: 		_configContext.WindowManager.WindowUnregistered += WindowManager_WindowUnregistered;
81
82  		// Initialize each of the workspaces.
83  		foreach (IWorkspace workspace in _workspaces)

Keep events for plugins to subscribe to changes.