remove util.OptionalBool and related functions (#29513)

and migrate affected code

_last refactoring bits to replace **util.OptionalBool** with
**optional.Option[bool]**_

(cherry picked from commit a3f05d0d98408bb47333b19f505b21afcefa9e7c)

Conflicts:
	services/repository/branch.go
	trivial context conflict

services/auth/source/oauth2/init.go

@@ -12,8 +12,8 @@ import (
 	"code.gitea.io/gitea/models/auth"
 	"code.gitea.io/gitea/models/db"
 	"code.gitea.io/gitea/modules/log"
+	"code.gitea.io/gitea/modules/optional"
 	"code.gitea.io/gitea/modules/setting"
-	"code.gitea.io/gitea/modules/util"
 
 	"github.com/google/uuid"
 	"github.com/gorilla/sessions"
@@ -66,7 +66,7 @@ func ResetOAuth2(ctx context.Context) error {
 // initOAuth2Sources is used to load and register all active OAuth2 providers
 func initOAuth2Sources(ctx context.Context) error {
 	authSources, err := db.Find[auth.Source](ctx, auth.FindSourcesOptions{
-		IsActive:  util.OptionalBoolTrue,
+		IsActive:  optional.Some(true),
 		LoginType: auth.OAuth2,
 	})
 	if err != nil {