Merge bitcoin/bitcoin#31958: rpc: add cli examples, update docs

32dcec2 rpc: update RPC help of `createpsbt` (rkrux)
931117a rpc: update the doc for `data` field in `outputs` argument (rkrux)
8134a6b rpc: add cli example for `walletcreatefundedpsbt` RPC (rkrux)

Pull request description:

  ### add cli example for `walletcreatefundedpsbt` and `createpsbt` RPCs
  The only example present earlier was one that creates an OP_RETURN output. This
      lack of examples has discouraged me earlier to use this RPC. Adding an example
      that creates PSBT sending bitcoin to address, a scenario that is much more common.

  ### rpc: update the doc for `data` field in `outputs` argument
  It was not evident to me that this field creates an `OP_RETURN` output until
      I read the code and tried it out. Thus, making the doc explicitly mention it.
  This affects docs of the following RPCs:
  `bumpfee`, `psbtbumpfee`, `send`, `walletcreatefundedpsbt`, `createpsbt`,
  and `createrawtransaction`

ACKs for top commit:
  sipa:
    utACK 32dcec2
  1440000bytes:
    utACK bitcoin/bitcoin@32dcec2
  achow101:
    ACK 32dcec2
  ryanofsky:
    Concept ACK 32dcec2. These seem like helpful clarifications, but I did not look into the details

Tree-SHA512: f994488ba7d52d00960fc52064bb419cf548e29822fe23d6ee0452fdf514dd93f089145eddb32b8086a7918cf8cf33a4c3f16bfcb7948f3c9d5afd95e8d3a1cb

Author: achow101

src/rpc/rawtransaction.cpp

@@ -150,7 +150,7 @@ static std::vector<RPCArg> CreateTxDoc()
                 },
                 {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "",
                     {
-                        {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data"},
+                        {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data that becomes a part of an OP_RETURN output"},
                     },
                 },
             },
@@ -1550,13 +1550,15 @@ static RPCHelpMan createpsbt()
 {
     return RPCHelpMan{"createpsbt",
                 "\nCreates a transaction in the Partially Signed Transaction format.\n"
-                "Implements the Creator role.\n",
+                "Implements the Creator role.\n"
+                "Note that the transaction's inputs are not signed, and\n"
+                "it is not stored in the wallet or transmitted to the network.\n",
                 CreateTxDoc(),
                 RPCResult{
                     RPCResult::Type::STR, "", "The resulting raw transaction (base64-encoded string)"
                 },
                 RPCExamples{
-                    HelpExampleCli("createpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+                    HelpExampleCli("createpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"address\\\":0.01}]\"")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {

src/wallet/rpc/spend.cpp

@@ -983,7 +983,7 @@ static std::vector<RPCArg> OutputsDoc()
         },
         {"", RPCArg::Type::OBJ, RPCArg::Optional::OMITTED, "",
             {
-                {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data"},
+                {"data", RPCArg::Type::STR_HEX, RPCArg::Optional::NO, "A key-value pair. The key must be \"data\", the value is hex-encoded data that becomes a part of an OP_RETURN output"},
             },
         },
     };
@@ -1734,8 +1734,10 @@ RPCHelpMan walletcreatefundedpsbt()
                     }
                                 },
                                 RPCExamples{
-                            "\nCreate a transaction with no inputs\n"
-                            + HelpExampleCli("walletcreatefundedpsbt", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+                            "\nCreate a PSBT with automatically picked inputs that sends 0.5 BTC to an address and has a fee rate of 2 sat/vB:\n"
+                            + HelpExampleCli("walletcreatefundedpsbt", "\"[]\" \"[{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.5}]\" 0 \"{\\\"add_inputs\\\":true,\\\"fee_rate\\\":2}\"")
+                            + "\nCreate the same PSBT as the above one instead using named arguments:\n"
+                            + HelpExampleCli("-named walletcreatefundedpsbt", "outputs=\"[{\\\"" + EXAMPLE_ADDRESS[0] + "\\\":0.5}]\" add_inputs=true fee_rate=2")
                                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {