Merge bitcoin/bitcoin#18448: rpc: fix/add missing RPCExamples for "Util" RPCs

ea98d9c2ef rpc: fix/add missing RPCExamples for "Util" RPCs (Sebastian Falbesoner)

Pull request description:

  Similar to https://github.com/bitcoin/bitcoin/pull/18398, this PR gives the RPCExamples in the RPC category "Util" (that currently contains `createmultisig`, `deriveaddresses`, `estimatesmartfee`, `getdescriptorinfo`, `signmessagewithprivkey`, `validateaddress`, `verifymessage`) some love by fixing one broken and adding three missing examples:
  - fixed `HelpExampleRpc` for `createmultisig` (disturbing escape characters and quotation marks)
  - added missing `HelpExampleRpc` for
      -  `deriveaddresses` (also put descriptor in a new string constant)
      - `estimatesmartfee`
      - `getdescriptorinfo` (also put descriptor in a new string constant)

  Output for `createmultisig` example on the master branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, "[\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\",\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\"]"]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":null,"error":{"code":-1,"message":"JSON value is not an array as expected"},"id":"curltest"}
  ```

  Output for `createmultisig` example on the PR branch:
  ```
  $ curl --user __cookie__ --data-binary '{"jsonrpc": "1.0", "id": "curltest", "method": "createmultisig", "params": [2, ["03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd","03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626"]]}' -H 'content-type: text/plain;' http://127.0.0.1:8332/
  Enter host password for user '__cookie__':
  {"result":{"address":"3QsFXpFJf2ZY6GLWVoNFFd2xSDwdS713qX","redeemScript":"522103789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd2103dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a6162652ae","descriptor":"sh(multi(2,03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd,03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626))#4djp057k"},"error":null,"id":"curltest"}
  ```

ACKs for top commit:
  jonatack:
    ACK ea98d9c2ef looked at the code, rebased to master, ran the helps, did not try running the added json-rpc examples

Tree-SHA512: d6ecb6da66f19517065453357d210102e2cc9f1f8037aeb6a9177ff036d0c21773dddf5e0acdbc71edbbde3026e4d1e7ce7c0935cd3e023c60f34e1b173b3299

src/rpc/mining.cpp

@@ -1089,7 +1089,8 @@ static RPCHelpMan estimatesmartfee()
             "have been observed to make an estimate for any number of blocks."},
                     }},
                 RPCExamples{
-                    HelpExampleCli("estimatesmartfee", "6")
+                    HelpExampleCli("estimatesmartfee", "6") +
+                    HelpExampleRpc("estimatesmartfee", "6")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {

src/rpc/misc.cpp

@@ -109,7 +109,7 @@ static RPCHelpMan createmultisig()
             "\nCreate a multisig address from 2 public keys\n"
             + HelpExampleCli("createmultisig", "2 \"[\\\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\\\",\\\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\\\"]\"") +
             "\nAs a JSON-RPC call\n"
-            + HelpExampleRpc("createmultisig", "2, \"[\\\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\\\",\\\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\\\"]\"")
+            + HelpExampleRpc("createmultisig", "2, [\"03789ed0bb717d88f7d321a368d905e7430207ebbd82bd342cf11ae157a7ace5fd\",\"03dbc6764b8884a92e871274b87583e6d5c2a58819473e17e107ef3f6aa5a61626\"]")
                 },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
@@ -158,6 +158,8 @@ static RPCHelpMan createmultisig()
 
 static RPCHelpMan getdescriptorinfo()
 {
+    const std::string EXAMPLE_DESCRIPTOR = "wpkh([d34db33f/84h/0h/0h]0279be667ef9dcbbac55a06295Ce870b07029Bfcdb2dce28d959f2815b16f81798)";
+
     return RPCHelpMan{"getdescriptorinfo",
             {"\nAnalyses a descriptor.\n"},
             {
@@ -175,7 +177,8 @@ static RPCHelpMan getdescriptorinfo()
             },
             RPCExamples{
                 "Analyse a descriptor\n" +
-                HelpExampleCli("getdescriptorinfo", "\"wpkh([d34db33f/84h/0h/0h]0279be667ef9dcbbac55a06295Ce870b07029Bfcdb2dce28d959f2815b16f81798)\"")
+                HelpExampleCli("getdescriptorinfo", "\"" + EXAMPLE_DESCRIPTOR + "\"") +
+                HelpExampleRpc("getdescriptorinfo", "\"" + EXAMPLE_DESCRIPTOR + "\"")
             },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {
@@ -201,6 +204,8 @@ static RPCHelpMan getdescriptorinfo()
 
 static RPCHelpMan deriveaddresses()
 {
+    const std::string EXAMPLE_DESCRIPTOR = "wpkh([d34db33f/84h/0h/0h]xpub6DJ2dNUysrn5Vt36jH2KLBT2i1auw1tTSSomg8PhqNiUtx8QX2SvC9nrHu81fT41fvDUnhMjEzQgXnQjKEu3oaqMSzhSrHMxyyoEAmUHQbY/0/*)#cjjspncu";
+
     return RPCHelpMan{"deriveaddresses",
             {"\nDerives one or more addresses corresponding to an output descriptor.\n"
             "Examples of output descriptors are:\n"
@@ -223,7 +228,8 @@ static RPCHelpMan deriveaddresses()
             },
             RPCExamples{
                 "First three native segwit receive addresses\n" +
-                HelpExampleCli("deriveaddresses", "\"wpkh([d34db33f/84h/0h/0h]xpub6DJ2dNUysrn5Vt36jH2KLBT2i1auw1tTSSomg8PhqNiUtx8QX2SvC9nrHu81fT41fvDUnhMjEzQgXnQjKEu3oaqMSzhSrHMxyyoEAmUHQbY/0/*)#cjjspncu\" \"[0,2]\"")
+                HelpExampleCli("deriveaddresses", "\"" + EXAMPLE_DESCRIPTOR + "\" \"[0,2]\"") +
+                HelpExampleRpc("deriveaddresses", "\"" + EXAMPLE_DESCRIPTOR + "\", \"[0,2]\"")
             },
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
 {