Declarative plugin management (#2180)

* Declarative plugin management

Allow declaring `plugin` entries in the hyprland configuration.

Plugins will be loaded if an entry is added and unloaded if that entry
is removed.

* Replace pointers with copying in updateconfigPlugins

* Include which plugin was declared twice in error

src/Compositor.cpp

@@ -402,6 +402,7 @@ void CCompositor::initManagers(eManagersInitStage stage) {
 
             Debug::log(LOG, "Creating the PluginSystem!");
             g_pPluginSystem = std::make_unique<CPluginSystem>();
+            g_pConfigManager->handlePluginLoads();
         } break;
         default: UNREACHABLE();
     }