[feature] support processing of (many) more media types (#3090)

* initial work replacing our media decoding / encoding pipeline with ffprobe + ffmpeg

* specify the video codec to use when generating static image from emoji

* update go-storage library (fixes incompatibility after updating go-iotools)

* maintain image aspect ratio when generating a thumbnail for it

* update readme to show go-ffmpreg

* fix a bunch of media tests, move filesize checking to callers of media manager for more flexibility

* remove extra debug from error message

* fix up incorrect function signatures

* update PutFile to just use regular file copy, as changes are file is on separate partition

* fix remaining tests, remove some unneeded tests now we're working with ffmpeg/ffprobe

* update more tests, add more code comments

* add utilities to generate processed emoji / media outputs

* fix remaining tests

* add test for opus media file, add license header to utility cmds

* limit the number of concurrently available ffmpeg / ffprobe instances

* reduce number of instances

* further reduce number of instances

* fix envparsing test with configuration variables

* update docs and configuration with new media-{local,remote}-max-size variables

vendor/codeberg.org/gruf/go-iotools/write.go

@@ -28,7 +28,10 @@ func WriteCloser(w io.Writer, c io.Closer) io.WriteCloser {
 
 // NopWriteCloser wraps an io.Writer to implement io.WriteCloser with empty io.Closer implementation.
 func NopWriteCloser(w io.Writer) io.WriteCloser {
-	return WriteCloser(w, CloserFunc(func() error {
-		return nil
-	}))
+	return &nopWriteCloser{w}
 }
+
+// nopWriteCloser implements io.WriteCloser with a no-op Close().
+type nopWriteCloser struct{ io.Writer }
+
+func (wc *nopWriteCloser) Close() error { return nil }