[Backend] Stream mining and wallet events to front-end

[CjS77]

Provide a new Tauri event stream that provides the following events.

• transaction received
• transaction sent
• transaction cancelled
• transaction mined but unconfirmed
• transaction mined and confirmed
• New block mined

[alex1307]

All events above are streamed to the launchpad front-end. Should be closed.

[tarnas14]

implemented in two PRs:

238

246