Include confirmation depth and maybe other txn metadata in `z_getoperation{status,result}`.

[Nathan Wilcox]

Is your feature request related to a problem? Please describe.

Whenever I use z_sendmany, I want to check the operation status to see if there is a txid. When there is a txid, I almost always want to know how many confirmations it has, so I end up using gettransaction. It's a bit tedious to cut'n'paste and parse output (either visually or with a script).

Describe the solution you'd like

It would be nice if z_sendmany included this directly in the result. Perhaps something like this:

{
  …
  "result": {"txid": …, "confirmations": …},
  …
}

Alternatives you've considered

An alternative might be a higher-level API or client tool that just automates using z_getoperation{status|result} then subsequently looking up confirmations for the txns. This could be completely separate from zcashd, which is also appealing.

Additional context

Since we're likely to retire zcashd maintenance, I'm not sure how worthwhile this is, but it seems easy to implement. This ticket may be useful for other cli wallet implementors.