Provide a signal to pause/resume a running incremental snapshot

Since incremental snapshot is a resumable process, I'd like to suggest 2 additional signals (similarly to stop-snapshot): pause-snapshot and resume-snapshot.

The reason I'm suggesting that is because it seems that incremental snapshot can slow down the connector's performance and increases latency of emitted CDC events. So it'd be nice to have the option to pause the snapshot on certain time frames when latency isn't permitted.

I've been testing incremental snapshots recently (using MySQL connector, version 1.8.0.Final) and was measuring about 10-40 seconds of MilliSecondsBehindSource metric while the snapshot was running (vs. less than a second before running it).