refactor: move media channel handling to common/ and setup duplex channel

a duplex media channel should be more realistic, you generally both send and receive media when doing video call and
stuff

client/lib/util.go

@@ -1,9 +1,7 @@
 package snowflake_client
 
 import (
-	"crypto/rand"
 	"log"
-	"math/big"
 	"time"
 )
 
@@ -71,12 +69,3 @@ func (b *bytesSyncLogger) addOutbound(amount int64) {
 func (b *bytesSyncLogger) addInbound(amount int64) {
 	b.inboundChan <- amount
 }
-
-func randomInt(min, max int) int {
-	nBig, err := rand.Int(rand.Reader, big.NewInt(int64(max-min)))
-	if err != nil {
-		panic(err)
-	}
-
-	return int(nBig.Int64()) + min
-}