Rewrite queue (#24505)

# ⚠️ Breaking

Many deprecated queue config options are removed (actually, they should
have been removed in 1.18/1.19).

If you see the fatal message when starting Gitea: "Please update your
app.ini to remove deprecated config options", please follow the error
messages to remove these options from your app.ini.

Example:

```
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].ISSUE_INDEXER_QUEUE_TYPE`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [E] Removed queue option: `[indexer].UPDATE_BUFFER_LEN`. Use new options in `[queue.issue_indexer]`
2023/05/06 19:39:22 [F] Please update your app.ini to remove deprecated config options
```

Many options in `[queue]` are are dropped, including:
`WRAP_IF_NECESSARY`, `MAX_ATTEMPTS`, `TIMEOUT`, `WORKERS`,
`BLOCK_TIMEOUT`, `BOOST_TIMEOUT`, `BOOST_WORKERS`, they can be removed
from app.ini.

# The problem

The old queue package has some legacy problems:

* complexity: I doubt few people could tell how it works.
* maintainability: Too many channels and mutex/cond are mixed together,
too many different structs/interfaces depends each other.
* stability: due to the complexity & maintainability, sometimes there
are strange bugs and difficult to debug, and some code doesn't have test
(indeed some code is difficult to test because a lot of things are mixed
together).
* general applicability: although it is called "queue", its behavior is
not a well-known queue.
* scalability: it doesn't seem easy to make it work with a cluster
without breaking its behaviors.

It came from some very old code to "avoid breaking", however, its
technical debt is too heavy now. It's a good time to introduce a better
"queue" package.

# The new queue package

It keeps using old config and concept as much as possible.

* It only contains two major kinds of concepts:
    * The "base queue": channel, levelqueue, redis
* They have the same abstraction, the same interface, and they are
tested by the same testing code.
* The "WokerPoolQueue", it uses the "base queue" to provide "worker
pool" function, calls the "handler" to process the data in the base
queue.
* The new code doesn't do "PushBack"
* Think about a queue with many workers, the "PushBack" can't guarantee
the order for re-queued unhandled items, so in new code it just does
"normal push"
* The new code doesn't do "pause/resume"
* The "pause/resume" was designed to handle some handler's failure: eg:
document indexer (elasticsearch) is down
* If a queue is paused for long time, either the producers blocks or the
new items are dropped.
* The new code doesn't do such "pause/resume" trick, it's not a common
queue's behavior and it doesn't help much.
* If there are unhandled items, the "push" function just blocks for a
few seconds and then re-queue them and retry.
* The new code doesn't do "worker booster"
* Gitea's queue's handlers are light functions, the cost is only the
go-routine, so it doesn't make sense to "boost" them.
* The new code only use "max worker number" to limit the concurrent
workers.
* The new "Push" never blocks forever
* Instead of creating more and more blocking goroutines, return an error
is more friendly to the server and to the end user.

There are more details in code comments: eg: the "Flush" problem, the
strange "code.index" hanging problem, the "immediate" queue problem.

Almost ready for review.

TODO:

* [x] add some necessary comments during review
* [x] add some more tests if necessary
* [x] update documents and config options
* [x] test max worker / active worker
* [x] re-run the CI tasks to see whether any test is flaky
* [x] improve the `handleOldLengthConfiguration` to provide more
friendly messages
* [x] fine tune default config values (eg: length?)

## Code coverage:

![image](https://user-images.githubusercontent.com/2114189/236620635-55576955-f95d-4810-b12f-879026a3afdf.png)

2 files changed, 9 insertions, 15 deletions

diff --git a/services/repository/archiver/archiver.go b/services/repository/archiver/archiver.go
index 1da4425cfc..1c514a4112 100644
--- a/services/repository/archiver/archiver.go
+++ b/services/repository/archiver/archiver.go
@@ -295,26 +295,21 @@ func ArchiveRepository(request *ArchiveRequest) (*repo_model.RepoArchiver, error
 	return doArchive(request)
 }
 
-var archiverQueue queue.UniqueQueue
+var archiverQueue *queue.WorkerPoolQueue[*ArchiveRequest]
 
 // Init initlize archive
 func Init() error {
-	handler := func(data ...queue.Data) []queue.Data {
-		for _, datum := range data {
-			archiveReq, ok := datum.(*ArchiveRequest)
-			if !ok {
-				log.Error("Unable to process provided datum: %v - not possible to cast to IndexerData", datum)
-				continue
-			}
+	handler := func(items ...*ArchiveRequest) []*ArchiveRequest {
+		for _, archiveReq := range items {
 			log.Trace("ArchiverData Process: %#v", archiveReq)
 			if _, err := doArchive(archiveReq); err != nil {
-				log.Error("Archive %v failed: %v", datum, err)
+				log.Error("Archive %v failed: %v", archiveReq, err)
 			}
 		}
 		return nil
 	}
 
-	archiverQueue = queue.CreateUniqueQueue("repo-archive", handler, new(ArchiveRequest))
+	archiverQueue = queue.CreateUniqueQueue("repo-archive", handler)
 	if archiverQueue == nil {
 		return errors.New("unable to create codes indexer queue")
 	}
diff --git a/services/repository/push.go b/services/repository/push.go
index 7f174c71b3..c7ea8f336e 100644
--- a/services/repository/push.go
+++ b/services/repository/push.go
@@ -29,12 +29,11 @@ import (
 )
 
 // pushQueue represents a queue to handle update pull request tests
-var pushQueue queue.Queue
+var pushQueue *queue.WorkerPoolQueue[[]*repo_module.PushUpdateOptions]
 
 // handle passed PR IDs and test the PRs
-func handle(data ...queue.Data) []queue.Data {
-	for _, datum := range data {
-		opts := datum.([]*repo_module.PushUpdateOptions)
+func handler(items ...[]*repo_module.PushUpdateOptions) [][]*repo_module.PushUpdateOptions {
+	for _, opts := range items {
 		if err := pushUpdates(opts); err != nil {
 			log.Error("pushUpdate failed: %v", err)
 		}
@@ -43,7 +42,7 @@ func handle(data ...queue.Data) []queue.Data {
 }
 
 func initPushQueue() error {
-	pushQueue = queue.CreateQueue("push_update", handle, []*repo_module.PushUpdateOptions{})
+	pushQueue = queue.CreateSimpleQueue("push_update", handler)
 	if pushQueue == nil {
 		return errors.New("unable to create push_update Queue")
 	}