Support using label names when changing issue labels (#30943)

Resolve #30917

Make the APIs for adding labels and replacing labels support both label
IDs and label names so the
[`actions/labeler`](https://github.com/actions/labeler) action can work
in Gitea.

<img width="600px"
src="7835c771-f637-4c57-9ce5-e4fbf56fa0d3"
/>

modules/structs/issue_label.go

@@ -47,8 +47,9 @@ type EditLabelOption struct {
 
 // IssueLabelsOption a collection of labels
 type IssueLabelsOption struct {
-	// list of label IDs
-	Labels []int64 `json:"labels"`
+	// Labels can be a list of integers representing label IDs
+	// or a list of strings representing label names
+	Labels []any `json:"labels"`
 }
 
 // LabelTemplate info of a Label template