[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>

vendor/codeberg.org/gruf/go-runners/process.go

@@ -0,0 +1,75 @@
+package runners
+
+import (
+	"fmt"
+	"sync"
+)
+
+// Processable defines a runnable process with error return
+// that can be passed to a Processor instance for managed running.
+type Processable func() error
+
+// Processor acts similarly to a sync.Once object, except that it is reusable. After
+// the first call to Process(), any further calls before this first has returned will
+// block until the first call has returned, and return the same error. This ensures
+// that only a single instance of it is ever running at any one time.
+type Processor struct {
+	mutex sync.Mutex
+	state uint32
+	wait  sync.WaitGroup
+	err   *error
+}
+
+// Process will process the given function if first-call, else blocking until
+// the first function has returned, returning the same error result.
+func (p *Processor) Process(proc Processable) (err error) {
+	// Acquire state lock.
+	p.mutex.Lock()
+
+	if p.state != 0 {
+		// Already running.
+		//
+		// Get current err ptr.
+		errPtr := p.err
+
+		// Wait until finish.
+		p.mutex.Unlock()
+		p.wait.Wait()
+		return *errPtr
+	}
+
+	// Reset error ptr.
+	p.err = new(error)
+
+	// Set started.
+	p.wait.Add(1)
+	p.state = 1
+	p.mutex.Unlock()
+
+	defer func() {
+		if r := recover(); r != nil {
+			if err != nil {
+				rOld := r // wrap the panic so we don't lose existing returned error
+				r = fmt.Errorf("panic occured after error %q: %v", err.Error(), rOld)
+			}
+
+			// Catch any panics and wrap as error.
+			err = fmt.Errorf("caught panic: %v", r)
+		}
+
+		// Store error.
+		*p.err = err
+
+		// Mark done.
+		p.wait.Done()
+
+		// Set stopped.
+		p.mutex.Lock()
+		p.state = 0
+		p.mutex.Unlock()
+	}()
+
+	// Run process.
+	err = proc()
+	return
+}