Move issues related files into models/issues (#19931)

* Move access and repo permission to models/perm/access

* fix test

* fix git test

* Move functions sequence

* Some improvements per @KN4CK3R and @delvh

* Move issues related code to models/issues

* Move some issues related sub package

* Merge

* Fix test

* Fix test

* Fix test

* Fix test

* Rename some files

models/migrations/v111.go

@@ -131,7 +131,7 @@ func addBranchProtectionCanPushAndEnableWhitelist(x *xorm.Engine) error {
 		Authorize int
 	}
 
-	// getUserRepoPermission static function based on models.IsOfficialReviewer at 5d78792385
+	// getUserRepoPermission static function based on issues_model.IsOfficialReviewer at 5d78792385
 	getUserRepoPermission := func(sess *xorm.Session, repo *Repository, user *User) (Permission, error) {
 		var perm Permission