multi: Increase proof-delivery fault tolerance with proof-courier optimizations

[dstadulis]

In discussing optimizations regarding #1009
Various proof delivery optimization ideas were discussed:

• Hasten more transaction-validation steps, prior to transaction broadcast
• Add transaction-generation fault if malformed proof-courier addresses provided
• Ensuring proof courier is aware of successful proof transmission
  • Log on each proof's output / Decide on logging location in DB
• Add Proof-delivery fail-over / fallback method (Weigh UX needs: Upload to public universe to promote asset receiving vs being uncompromising on users' proof delivery privacy preferences: add method to perform subsequent delivery of proof if contacted by recipient )

[guggero]

I think all these TODO items either have been addressed or are tracked in other issues.