Merge bitcoin#27829: rpc: fix data optionality for RPC calls.

27b168b Update help text for spend and rawtransaction rpcs (Michael Tidwell)

Pull request description:

  The "data" field without outputs was marked as "required" in the help docs when using bitcoin-cli. This field when left off worked as an intended optional OP_RETURN. closes bitcoin#27828.

  Motivation: It is hard to understand that "data" is actually optional for commands like `createpsbt` and `walletcreatefundedpsbt`.

ACKs for top commit:
  achow101:
    ACK 27b168b
  Sjors:
    tACK 27b168b

Tree-SHA512: 235e7ed4af69880880c04015b3f7de72c8f31ae035485c4c64c483e282948f3ea3f1eef16f15e260a1aaf21114150713516ba6a99967ccad9ecd91ff67cb0450

Author: achow101

src/rpc/rawtransaction.cpp

@@ -199,8 +199,9 @@ static std::vector<RPCArg> CreateTxDoc()
                 },
             },
         },
-        {"outputs", RPCArg::Type::ARR, RPCArg::Optional::NO, "The outputs (key-value pairs), where none of the keys are duplicated.\n"
-                "That is, each address can only appear once and there can only be one 'data' object.\n"
+        {"outputs", RPCArg::Type::ARR, RPCArg::Optional::NO, "The outputs specified as key-value pairs.\n"
+                "Each key may only appear once, i.e. there can only be one 'data' output, and no address may be duplicated.\n"
+                "At least one output of either type must be specified.\n"
                 "For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
                 "                             accepted as second parameter.",
             {

src/wallet/rpc/spend.cpp

@@ -803,8 +803,9 @@ RPCHelpMan send()
         "\nEXPERIMENTAL warning: this call may be changed in future releases.\n"
         "\nSend a transaction.\n",
         {
-            {"outputs", RPCArg::Type::ARR, RPCArg::Optional::NO, "The outputs (key-value pairs), where none of the keys are duplicated.\n"
-                    "That is, each address can only appear once and there can only be one 'data' object.\n"
+            {"outputs", RPCArg::Type::ARR, RPCArg::Optional::NO, "The outputs specified as key-value pairs.\n"
+                    "Each key may only appear once, i.e. there can only be one 'data' output, and no address may be duplicated.\n"
+                    "At least one output of either type must be specified.\n"
                     "For convenience, a dictionary, which holds the key-value pairs directly, is also accepted.",
                 {
                     {"", RPCArg::Type::OBJ_USER_KEYS, RPCArg::Optional::OMITTED, "",