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"
/>

(cherry picked from commit b3beaed147466739de0c24fd80206b5af8b71617)

Conflicts:
	- modules/structs/issue_label.go
	  Resolved by applying the Gitea change by hand.
	- tests/integration/api_issue_label_test.go
	  Resolved by copying the new tests.

modules/structs/issue_label.go

@@ -57,8 +57,9 @@ type DeleteLabelsOption 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"`
 	// swagger:strfmt date-time
 	Updated *time.Time `json:"updated_at"`
 }