[performance] processing media and scheduled jobs improvements (#1482)

* replace media workers with just runners.WorkerPool, move to state structure, use go-sched for global task scheduling

* improved code comment

* fix worker tryUntil function, update go-runners/go-sched

* make preprocess functions package public, use these where possible to stop doubled up processing

* remove separate emoji worker pool

* limit calls to time.Now() during media preprocessing

* use Processor{} to manage singular runtime of processing media

* ensure workers get started when media manager is used

* improved error setting in processing media, fix media test

* port changes from processingmedia to processing emoji

* finish code commenting

* finish code commenting and comment-out client API + federator worker pools until concurrency worker pools replaced

* linterrrrrrrrrrrrrrrr

---------

Signed-off-by: kim <grufwub@gmail.com>

internal/processing/media/getfile.go

@@ -159,7 +159,7 @@ func (p *processor) getAttachmentContent(ctx context.Context, requestingAccount
 		}
 
 		// Start recaching this media with the prepared data function.
-		processingMedia, err := p.mediaManager.RecacheMedia(ctx, dataFn, nil, wantedMediaID)
+		processingMedia, err := p.mediaManager.PreProcessMediaRecache(ctx, dataFn, nil, wantedMediaID)
 		if err != nil {
 			return nil, gtserror.NewErrorNotFound(fmt.Errorf("error recaching media: %s", err))
 		}