Revert PluginCore use of event listening for current LogMonitor state (#64)

The order that listeners get notified isn't deterministic and as a result plugins which read the current state from PluginCore during the handling of a state change event may read a stale state resulting in unexpected results. PluginCore now reads a property directly from LogMonitor to avoid such inconsistencies.

ObservatoryCore/PluginManagement/PluginManager.cs

@@ -49,7 +49,6 @@ namespace Observatory.PluginManagement
             logMonitor.LogMonitorStateChanged += pluginHandler.OnLogMonitorStateChanged;
 
             var core = new PluginCore();
-            logMonitor.LogMonitorStateChanged += core.OnLogMonitorStateChanged;
 
             List<IObservatoryPlugin> errorPlugins = new();