Pause queues (#15928)

* Start adding mechanism to return unhandled data

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Create pushback interface

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add Pausable interface to WorkerPool and Manager

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Implement Pausable and PushBack for the bytefifos

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Implement Pausable and Pushback for ChannelQueues and ChannelUniqueQueues

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Wire in UI for pausing

Signed-off-by: Andrew Thornton <art27@cantab.net>

* add testcases and fix a few issues

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix build

Signed-off-by: Andrew Thornton <art27@cantab.net>

* prevent "race" in the test

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix jsoniter mismerge

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix conflicts

Signed-off-by: Andrew Thornton <art27@cantab.net>

* fix format

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Add warnings for no worker configurations and prevent data-loss with redis/levelqueue

Signed-off-by: Andrew Thornton <art27@cantab.net>

* Use StopTimer

Signed-off-by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lauris BH <lauris@nix.lv>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

routers/web/web.go

@@ -402,6 +402,8 @@ func RegisterRoutes(m *web.Route) {
 				m.Post("/add", admin.AddWorkers)
 				m.Post("/cancel/{pid}", admin.WorkerCancel)
 				m.Post("/flush", admin.Flush)
+				m.Post("/pause", admin.Pause)
+				m.Post("/resume", admin.Resume)
 			})
 		})