ffd09281fe26446fcefa0627c220a52706e35227 rpc: various fixups for dumptxoutset (James O'Beirne)
Pull request description:
This is part of the [assumeutxo project](https://github.com/bitcoin/bitcoin/projects/11) (parent PR: #15606)
---
A few fixes to make this RPC actually useful when generating snapshots.
- Generate an assumeutxo hash and display it (sort of a bugfix)
- Add nchaintx to output (necessary for use in chainparams entry)
- Add path of serialized UTXO file to output
ACKs for top commit:
laanwj:
Code review ACK ffd09281fe26446fcefa0627c220a52706e35227
Tree-SHA512: b0b5fd5138dea0e21258b1b18ab75bf3fd1628522cc1dbafa81af9cb9fa96562a1c39124fdb31057f256bfc560f462f907e9fe5e209b577b3f57afae2b7be826