fix(sec): permission check for project issue

- Do an access check when loading issues for a project column, currently
this is not done and exposes the title, labels and existence of a
private issue that the viewer of the project board may not have access
to.
- The number of issues cannot be calculated in a efficient manner
and stored in the database because their number may vary depending on
the visibility of the repositories participating in the project. The
previous implementation used the pre-calculated numbers stored in each
project, which did not reflect that potential variation.
- The code is derived from https://github.com/go-gitea/gitea/pull/22865

models/project/issue.go

@@ -34,20 +34,6 @@ func deleteProjectIssuesByProjectID(ctx context.Context, projectID int64) error
 	return err
 }
 
-// NumIssues return counter of all issues assigned to a project
-func (p *Project) NumIssues(ctx context.Context) int {
-	c, err := db.GetEngine(ctx).Table("project_issue").
-		Where("project_id=?", p.ID).
-		GroupBy("issue_id").
-		Cols("issue_id").
-		Count()
-	if err != nil {
-		log.Error("NumIssues: %v", err)
-		return 0
-	}
-	return int(c)
-}
-
 // NumClosedIssues return counter of closed issues assigned to a project
 func (p *Project) NumClosedIssues(ctx context.Context) int {
 	c, err := db.GetEngine(ctx).Table("project_issue").