Implement headers in Redis adapter

[icebob]

We should implement header support in Redis adapter as well. After it, all adapters support it and we can use it to send moleculer specific properties like tracing IDs. We can store it as serialized string after the payload:

            const id = await clientPub.xadd(
                channelName, // Stream name
                "*", // Auto ID
                "payload", // Entry
                opts.raw ? payload : this.serializer.serialize(payload) // Actual payload
                "headers",
                this.serializer.serialize(headers)
            );