MM-56082 Add PreferencesHaveChanged plugin hook (#25659)

* Add interface for PreferencesHaveChanged hook

* Add context to preference-related methods of App

* Implement PreferencesHaveChanged

* Re-add missing "fmt" import

* Update minimum server version for the new hook

* Remove pointers to be consistent with other preference APIs

server/public/plugin/plugintest/hooks.go

@@ -359,6 +359,11 @@ func (_m *Hooks) OnWebSocketDisconnect(webConnID string, userID string) {
 	_m.Called(webConnID, userID)
 }
 
+// PreferencesHaveChanged provides a mock function with given fields: c, preferences
+func (_m *Hooks) PreferencesHaveChanged(c *plugin.Context, preferences []model.Preference) {
+	_m.Called(c, preferences)
+}
+
 // ReactionHasBeenAdded provides a mock function with given fields: c, reaction
 func (_m *Hooks) ReactionHasBeenAdded(c *plugin.Context, reaction *model.Reaction) {
 	_m.Called(c, reaction)