Signal Tracking: update `connected` checks

[WillieHabi]

Description

In this PR we move the this.connected check from process to submission. If a signal is sent while the client is disconnected from the delta stream, we should not attempt to track the signal as we don't expect to receive it back. If a signal has been received, it follows that the client must've been connected to the delta stream to receive the message, so we don't need a connected check here.