Support changing labels of Actions runner without re-registration (#24806)

close #24540

related:
- Protocol: https://gitea.com/gitea/actions-proto-def/pulls/9
- Runner side: https://gitea.com/gitea/act_runner/pulls/201

changes:
- Add column of `labels` to table `action_runner`, and combine the value
of `agent_labels` and `custom_labels` column to `labels` column.
- Store `labels` when registering `act_runner`.
- Update `labels` when `act_runner` starting and calling `Declare`.
- Users cannot modify the `custom labels` in edit page any more.

other changes:
- Store `version` when registering `act_runner`.
- If runner is latest version, parse version from `Declare`. But older
version runner still parse version from request header.

models/migrations/v1_21/main_test.go

@@ -0,0 +1,14 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_21 //nolint
+
+import (
+	"testing"
+
+	"code.gitea.io/gitea/models/migrations/base"
+)
+
+func TestMain(m *testing.M) {
+	base.MainTest(m)
+}

models/migrations/v1_21/v260.go

@@ -0,0 +1,26 @@
+// Copyright 2023 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package v1_21 //nolint
+
+import (
+	"code.gitea.io/gitea/models/migrations/base"
+
+	"xorm.io/xorm"
+)
+
+func DropCustomLabelsColumnToActRunner(x *xorm.Engine) error {
+	sess := x.NewSession()
+	defer sess.Close()
+
+	if err := sess.Begin(); err != nil {
+		return err
+	}
+
+	// drop "custom_labels" cols
+	if err := base.DropTableColumns(sess, "action_runner", "custom_labels"); err != nil {
+		return err
+	}
+
+	return sess.Commit()
+}