[performance] convert enum strings to ints (#3558)

* convert statuses.visibility and notifications.notification_type columns from type string -> int for performance / space savings

* fix test trying to compare string to int

* fix instance count query using string literal instead of gtsmodel const type

* ensure a default value is always set

* also migrate the account settings and sin bin status tables

* initialize maps outside loops and place into singular enum mapping creation func

* use int16 for enum types

* update sinbinstatus creation to be from a snapshot at initial creation

* add snapshot of poll type at creation time

internal/processing/timeline/notification.go

@@ -41,8 +41,8 @@ func (p *Processor) NotificationsGet(
 	sinceID string,
 	minID string,
 	limit int,
-	types []string,
-	excludeTypes []string,
+	types []gtsmodel.NotificationType,
+	excludeTypes []gtsmodel.NotificationType,
 ) (*apimodel.PageableResponse, gtserror.WithCode) {
 	notifs, err := p.state.DB.GetAccountNotifications(
 		ctx,