MM-53355: tidy up plugins (#24194)

* remove feature flag managed plugins

* remove unneeded plugin blocklist

* remove unnecessary wrappers

* documentation and logging improvements

* avoid use of global logger
* leverage wrapped loggers (e.g. consistently log `plugin_id`)
* promote some logs from `Debug` to `Info` for better visibility.
* extract installPluginToFilestore
* rename some variables for consistency / clarity

* make generated

server/channels/app/cluster_handlers.go

@@ -16,7 +16,7 @@ func (s *Server) clusterInstallPluginHandler(msg *model.ClusterMessage) {
 	if jsonErr := json.Unmarshal(msg.Data, &data); jsonErr != nil {
 		mlog.Warn("Failed to decode from JSON", mlog.Err(jsonErr))
 	}
-	s.Channels().installPluginFromData(data)
+	s.Channels().installPluginFromClusterMessage(data.Id)
 }
 
 func (s *Server) clusterRemovePluginHandler(msg *model.ClusterMessage) {
@@ -24,7 +24,7 @@ func (s *Server) clusterRemovePluginHandler(msg *model.ClusterMessage) {
 	if jsonErr := json.Unmarshal(msg.Data, &data); jsonErr != nil {
 		mlog.Warn("Failed to decode from JSON", mlog.Err(jsonErr))
 	}
-	s.Channels().removePluginFromData(data)
+	s.Channels().removePluginFromClusterMessage(data.Id)
 }
 
 func (s *Server) clusterPluginEventHandler(msg *model.ClusterMessage) {