Move web JSON functions to web context and simplify code (#26132)

The JSONRedirect/JSONOK/JSONError functions were put into "Base" context
incorrectly, it would cause abuse.

Actually, they are for "web context" only, so, move them to the correct
place.

And by the way, use them to simplify old code: +75 -196

routers/web/shared/actions/runners.go

@@ -5,7 +5,6 @@ package actions
 
 import (
 	"errors"
-	"net/http"
 
 	actions_model "code.gitea.io/gitea/models/actions"
 	"code.gitea.io/gitea/models/db"
@@ -160,9 +159,7 @@ func RunnerDeletePost(ctx *context.Context, runnerID int64,
 		log.Warn("DeleteRunnerPost.UpdateRunner failed: %v, url: %s", err, ctx.Req.URL)
 		ctx.Flash.Warning(ctx.Tr("actions.runners.delete_runner_failed"))
 
-		ctx.JSON(http.StatusOK, map[string]any{
-			"redirect": failedRedirectTo,
-		})
+		ctx.JSONRedirect(failedRedirectTo)
 		return
 	}
 
@@ -170,7 +167,5 @@ func RunnerDeletePost(ctx *context.Context, runnerID int64,
 
 	ctx.Flash.Success(ctx.Tr("actions.runners.delete_runner_success"))
 
-	ctx.JSON(http.StatusOK, map[string]any{
-		"redirect": successRedirectTo,
-	})
+	ctx.JSONRedirect(successRedirectTo)
 }