MM-26753 Create initial sidebar categories on demand if migration hasn't ran (#14981)

* MM-26753 Change CreateInitialSidebarCategories to only take a user ID

* MM-26753 Create initial sidebar categories on demand if migration hasn't ran

* Wait for sidebar categories to be loaded in case of replication lag

store/store.go

@@ -217,7 +217,7 @@ type ChannelStore interface {
 	ClearAllCustomRoleAssignments() *model.AppError
 	MigratePublicChannels() error
 	MigrateSidebarCategories(fromTeamId, fromUserId string) (map[string]interface{}, error)
-	CreateInitialSidebarCategories(user *model.User, teamId string) error
+	CreateInitialSidebarCategories(userId, teamId string) error
 	MigrateFavoritesToSidebarChannels(lastUserId string, runningOrder int64) (map[string]interface{}, error)
 	GetSidebarCategories(userId, teamId string) (*model.OrderedSidebarCategories, *model.AppError)
 	GetSidebarCategory(categoryId string) (*model.SidebarCategoryWithChannels, *model.AppError)