[processing] Fix refreshing alg list does not refresh toolbox

Fix #16455, #16463

Author: nyalldawson

python/plugins/processing/gui/ProcessingToolbox.py

@@ -85,6 +85,10 @@ def openSettings(url):
 
         self.fillTree()
 
+        # connect to existing providers
+        for p in QgsApplication.processingRegistry().providers():
+            p.algorithmsLoaded.connect(self.updateProvider)
+
         QgsApplication.processingRegistry().providerRemoved.connect(self.removeProvider)
         QgsApplication.processingRegistry().providerAdded.connect(self.addProvider)
         settingsWatcher.settingsChanged.connect(self.fillTree)