use envelopeFeed to wait for envelopes to be available in tests (#1079)
use envelopeFeed to wait for envelopes to be available in tests (#1079)

* remove sleeps in WhisperMailboxSuite

* use envelopeFeed to wait for envelopes to be available in group chat test

* remove unsed envelopeTracer in whisper e2e tests

* unsubscribe from envelopeFeed

* use s.addPeerSync instead of WaitForPeerAsync

status-im/status-go,status-im/status-go,status-im/status-go