Merge #20944: rpc: Return total fee in getmempoolinfo

fa362064e3 rpc: Return total fee in mempool (MarcoFalke)

Pull request description:

  This avoids having to loop over the whole mempool to query each entry's fee

ACKs for top commit:
  achow101:
    ACK fa362064e3
  glozow:
    ACK https://github.com/bitcoin/bitcoin/pull/20944/commits/fa362064e383163a2585ffbc71ac1ea3bcc92663 🧸
  jnewbery:
    ACK fa362064e3

Tree-SHA512: e2fa1664df39c9e187f9229fc35764ccf436f6f75889c5a206d34fff473fc21efbf2bb143f4ca7895c27659218c22884d0ec4195e7a536a5a96973fc9dd82d08

doc/REST-interface.md

@@ -111,12 +111,7 @@ $ curl localhost:18332/rest/getutxos/checkmempool/b2cdfd7b89def827ff8af7cd9bff76
 
 Returns various information about the TX mempool.
 Only supports JSON as output format.
-* loaded : (boolean) if the mempool is fully loaded
-* size : (numeric) the number of transactions in the TX mempool
-* bytes : (numeric) size of the TX mempool in bytes
-* usage : (numeric) total TX mempool memory usage
-* maxmempool : (numeric) maximum memory usage for the mempool in bytes
-* mempoolminfee : (numeric) minimum feerate (BTC per KB) for tx to be accepted
+Refer to the `getmempoolinfo` RPC for documentation of the fields.
 
 `GET /rest/mempool/contents.json`