Display and update transactions in the Canton Coin Scan UI in terms of time, not Round number.

[waynecollier-da]

The current versions of Splice include a UI, Amulet Scan, which displays the history of recent transactions. This UI updates at each new round.

This creates an impression that rounds and transactions are related to each other, which is unfortunately misleading, since subcomponents of the same transaction could be recorded in different rounds.

We should modify the Scan UI to instead report as of record time, which is the basis for transaction sequencing. Each transaction in the UI should report its record time, and the UI should refresh regularly, on the order of two or three times per minute.

If not completed before this work, this work should also deprecate any endpoints that rely on round as an input, unless they are related directly to the process of recording activity and minting Amulet / Canton Coin.