MM-26410/MM-26825 Improve syncing between favorites category and preferences (#15048)

* MM-26410 Allow moving channels into Favorites when they're favorited in prefs

* MM-26410 Fix management of Favorites category when updating preferences

* MM-26410 Add management of Favorites category when deleting preferences

* Address feedback 1

* Remove WHERE (1=1) from query

* Remove unnecessary sq.Expr

* Rewrite query to use left join

* Remove redundant where statement and add some more tests

* Fix linting issues

* Rename addChannelToFavoritesCategory to addChannelToFavoritesCategory

store/store.go

@@ -225,7 +225,8 @@ type ChannelStore interface {
 	CreateSidebarCategory(userId, teamId string, newCategory *model.SidebarCategoryWithChannels) (*model.SidebarCategoryWithChannels, *model.AppError)
 	UpdateSidebarCategoryOrder(userId, teamId string, categoryOrder []string) *model.AppError
 	UpdateSidebarCategories(userId, teamId string, categories []*model.SidebarCategoryWithChannels) ([]*model.SidebarCategoryWithChannels, *model.AppError)
-	UpdateSidebarChannelsByPreferences(preferences *model.Preferences) *model.AppError
+	UpdateSidebarChannelsByPreferences(preferences *model.Preferences) error
+	DeleteSidebarChannelsByPreferences(preferences *model.Preferences) error
 	DeleteSidebarCategory(categoryId string) *model.AppError
 	GetAllChannelsForExportAfter(limit int, afterId string) ([]*model.ChannelForExport, *model.AppError)
 	GetAllDirectChannelsForExportAfter(limit int, afterId string) ([]*model.DirectChannelForExport, *model.AppError)