Improve queue & process & stacktrace (#24636)

Although some features are mixed together in this PR, this PR is not
that large, and these features are all related.

Actually there are more than 70 lines are for a toy "test queue", so
this PR is quite simple.

Major features:

1. Allow site admin to clear a queue (remove all items in a queue)
* Because there is no transaction, the "unique queue" could be corrupted
in rare cases, that's unfixable.
* eg: the item is in the "set" but not in the "list", so the item would
never be able to be pushed into the queue.
* Now site admin could simply clear the queue, then everything becomes
correct, the lost items could be re-pushed into queue by future
operations.
3. Split the "admin/monitor" to separate pages
4. Allow to download diagnosis report
* In history, there were many users reporting that Gitea queue gets
stuck, or Gitea's CPU is 100%
    * With diagnosis report, maintainers could know what happens clearly

The diagnosis report sample:
[gitea-diagnosis-20230510-192913.zip](https://github.com/go-gitea/gitea/files/11441346/gitea-diagnosis-20230510-192913.zip)
, use "go tool pprof profile.dat" to view the report.


Screenshots:


![image](https://github.com/go-gitea/gitea/assets/2114189/320659b4-2eda-4def-8dc0-5ea08d578063)


![image](https://github.com/go-gitea/gitea/assets/2114189/c5c46fae-9dc0-44ca-8cd3-57beedc5035e)


![image](https://github.com/go-gitea/gitea/assets/2114189/6168a811-42a1-4e64-a263-0617a6c8c4fe)

---------

Co-authored-by: Jason Song <i@wolfogre.com>
Co-authored-by: Giteabot <teabot@gitea.io>

routers/web/web.go

@@ -546,13 +546,16 @@ func registerRoutes(m *web.Route) {
 		})
 
 		m.Group("/monitor", func() {
-			m.Get("", admin.Monitor)
-			m.Get("/stacktrace", admin.GoroutineStacktrace)
-			m.Post("/cancel/{pid}", admin.MonitorCancel)
+			m.Get("/cron", admin.CronTasks)
+			m.Get("/stacktrace", admin.Stacktrace)
+			m.Post("/stacktrace/cancel/{pid}", admin.StacktraceCancel)
+			m.Get("/queue", admin.Queues)
 			m.Group("/queue/{qid}", func() {
-				m.Get("", admin.Queue)
+				m.Get("", admin.QueueManage)
 				m.Post("/set", admin.QueueSet)
+				m.Post("/remove-all-items", admin.QueueRemoveAllItems)
 			})
+			m.Get("/diagnosis", admin.MonitorDiagnosis)
 		})
 
 		m.Group("/users", func() {