[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-ffmpreg/util/funcs.go

@@ -0,0 +1,65 @@
+package util
+
+import (
+	"context"
+	"os"
+	"path"
+	"strconv"
+	"time"
+
+	"github.com/tetratelabs/wazero/api"
+)
+
+// Wasm_Tempnam wraps Go_Tempnam to fulfill wazero's api.GoModuleFunc,
+// the argument definition is (i32, i32) and return definition is (i32).
+// NOTE: the calling module MUST have access to exported malloc / free.
+func Wasm_Tempnam(ctx context.Context, mod api.Module, stack []uint64) {
+	dirptr := api.DecodeU32(stack[0])
+	pfxptr := api.DecodeU32(stack[1])
+	dir := readString(ctx, mod, dirptr, 0)
+	pfx := readString(ctx, mod, pfxptr, 0)
+	tmpstr := Go_Tempnam(dir, pfx)
+	tmpptr := writeString(ctx, mod, tmpstr)
+	stack[0] = api.EncodeU32(tmpptr)
+}
+
+// Go_Tempname is functionally similar to C's tempnam.
+func Go_Tempnam(dir, prefix string) string {
+	now := time.Now().Unix()
+	prefix = path.Join(dir, prefix)
+	for i := 0; i < 1000; i++ {
+		n := murmur2(uint32(now + int64(i)))
+		name := prefix + strconv.FormatUint(uint64(n), 10)
+		_, err := os.Stat(name)
+		if err == nil {
+			continue
+		} else if os.IsNotExist(err) {
+			return name
+		} else {
+			panic(err)
+		}
+	}
+	panic("too many attempts")
+}
+
+// murmur2 is a simple uint32 murmur2 hash
+// impl with fixed seed and input size.
+func murmur2(k uint32) (h uint32) {
+	const (
+		//  seed ^ bitlen
+		s = uint32(2147483647) ^ 8
+
+		M = 0x5bd1e995
+		R = 24
+	)
+	h = s
+	k *= M
+	k ^= k >> R
+	k *= M
+	h *= M
+	h ^= k
+	h ^= h >> 13
+	h *= M
+	h ^= h >> 15
+	return
+}