Additionally, accept a "now" timestamp, to allow avoiding rescans for keys
which are known never to have been used.
Note that the behavior when "now" is specified is slightly different than the
previous behavior when no timestamp was specified at all. Previously, when no
timestamp was specified, it would avoid rescanning during the importmulti call,
but set the key's nCreateTime value to 1, which would not prevent future block
reads in later ScanForWalletTransactions calls. With this change, passing a
"now" timestamp will set the key's nCreateTime to the current block time
instead of 1.
Fixes#9491
"\"scriptPubKey\": \"<script>\" | { \"address\":\"<address>\" }, (string / json, required) Type of scriptPubKey (string for script, json for address)\n"
"\"timestamp\": timestamp | \"now\" , (integer / string, required) Creation time of the key in seconds since epoch (Jan 1 1970 GMT),\n"
" or the string \"now\" to substitute the current synced blockchain time. The timestamp of the oldest\n"
" key will determine how far back blockchain rescans need to begin for missing wallet transactions.\n"
"\"now\" can be specified to bypass scanning, for keys which are known to never have been used, and\n"
" 0 can be specified to scan the entire blockchain.\n"
"\"redeemscript\": \"<script>\" , (string, optional) Allowed only if the scriptPubKey is a P2SH address or a P2SH scriptPubKey\n"
"\"pubkeys\": [\"<pubKey>\", ... ] , (array, optional) Array of strings giving pubkeys that must occur in the output or redeemscript\n"
"\"keys\": [\"<key>\", ... ] , (array, optional) Array of strings giving private keys whose corresponding public keys must occur in the output or redeemscript\n"
"\"internal\": <true> , (boolean, optional, default: false) Stating whether matching outputs should be be treated as not incoming payments\n"
"\"watchonly\": <true> , (boolean, optional, default: false) Stating whether matching outputs should be considered watched even when they're not spendable, only allowed if keys are empty\n"
"\"label\": <label> , (string, optional, default: '') Label to assign to the address (aka account name, for now), only allowed with internal=false\n"