[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/gtsmodel/interactionpolicy.go

@@ -224,7 +224,7 @@ func DefaultInteractionPolicyFor(v Visibility) *InteractionPolicy {
 	case VisibilityDirect:
 		return DefaultInteractionPolicyDirect()
 	default:
-		panic("visibility " + v + " not recognized")
+		panic("invalid visibility")
 	}
 }