Merge bitcoin/bitcoin#22021: rpc: bumpfee/psbtbumpfee fixes and updates

4f504f8 rpc: fix code comment for bumpfee/psbtbumpfee output (Jon Atack)
5cb7ac2 rpc: fix docs for bumpfee psbt update (Jon Atack)

Pull request description:

  Follow-up to #21544 and #20891 for the `bumpfee_helper` used for RPCs bumpfee and psbtbumpfee:
  - "psbt" field is only returned in psbtbumpfee and not bumpfee
  - bumpfee raises if private keys are disabled, so the txid help "Only returned when wallet private keys are enabled." no longer makes sense; remove it
  - add missing space in RPC examples ("Bump the fee, get the new transaction'stxid")
  - update txid/psbt code comments

ACKs for top commit:
  klementtan:
    ACK [`4f504f8`](bitcoin/bitcoin@4f504f8)

Tree-SHA512: 194faf8af52383eb8ac5cd22825265931bcde135dac79d8ecc4f84f698070da9b9373c00eef8623961881bb293157c7c9a0d71d1bcccf481ae3605a2d1444ed8

Author: MarcoFalke

src/wallet/rpcwallet.cpp

@@ -3430,12 +3430,10 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
                 "options"},
         },
         RPCResult{
-            RPCResult::Type::OBJ, "", "", Cat(Cat<std::vector<RPCResult>>(
-            {
-                {RPCResult::Type::STR, "psbt", "The base64-encoded unsigned PSBT of the new transaction."},
-            },
-            want_psbt ? std::vector<RPCResult>{} : std::vector<RPCResult>{{RPCResult::Type::STR_HEX, "txid", "The id of the new transaction. Only returned when wallet private keys are enabled."}}
-            ),
+            RPCResult::Type::OBJ, "", "", Cat(
+                want_psbt ?
+                std::vector<RPCResult>{{RPCResult::Type::STR, "psbt", "The base64-encoded unsigned PSBT of the new transaction."}} :
+                std::vector<RPCResult>{{RPCResult::Type::STR_HEX, "txid", "The id of the new transaction."}},
             {
                 {RPCResult::Type::STR_AMOUNT, "origfee", "The fee of the replaced transaction."},
                 {RPCResult::Type::STR_AMOUNT, "fee", "The fee of the new transaction."},
@@ -3446,7 +3444,7 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
             })
         },
         RPCExamples{
-    "\nBump the fee, get the new transaction\'s" + std::string(want_psbt ? "psbt" : "txid") + "\n" +
+    "\nBump the fee, get the new transaction\'s " + std::string(want_psbt ? "psbt" : "txid") + "\n" +
             HelpExampleCli(method_name, "<txid>")
         },
         [want_psbt](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
@@ -3528,8 +3526,8 @@ static RPCHelpMan bumpfee_helper(std::string method_name)
 
     UniValue result(UniValue::VOBJ);
 
-    // If wallet private keys are enabled, return the new transaction id,
-    // otherwise return the base64-encoded unsigned PSBT of the new transaction.
+    // For bumpfee, return the new transaction id.
+    // For psbtbumpfee, return the base64-encoded unsigned PSBT of the new transaction.
     if (!want_psbt) {
         if (!feebumper::SignTransaction(*pwallet, mtx)) {
             throw JSONRPCError(RPC_WALLET_ERROR, "Can't sign transaction.");