Merge #18531: rpc: remove deprecated CRPCCommand constructor

faaf9c58e4 remove CRPCCommand constructor that takes rpcfn_type function pointer (MarcoFalke)
fa19bb2cd8 remove dead rpc code (MarcoFalke)

Pull request description:

  Remove the CRPCCommand arguments, now that they are asserted to be equal and thus redundant

  ### Future work

  > Here or follow up, makes sense to also assert type of returned UniValue?

  Sure, but let's not get ahead of ourselves. I am going to submit any further works as follow-ups, including:

  * Removing all python regex linters on the args, now that RPCMan can be used to generate any output, including the cli.cpp table
  * Auto-formatting and sanity checking the RPCExamples with RPCMan
  * Checking passed-in json in self-check. Removing redundant checks
  * Checking returned json against documentation to avoid regressions or false documentation
  * Compile the RPC documentation at compile-time to ensure it doesn't change at runtime and is completely static

  ### Bugs found

  * The assert identified issue #18607
  * The changes itself fixed bug #19250

ACKs for top commit:
  fjahr:
    tested ACK faaf9c58e4
  promag:
    Tested ACK faaf9c58e4.
  ryanofsky:
    Code review ACK faaf9c58e4. Two obviously good simplifications.

Tree-SHA512: 5de3b440f7b2ed2c3e86655d4f0e2e5df9c67e8ce3c7817d5ea5311d1a38690f2f3e28fab41aad6936be9fc884326d037e5f19e85d4d2fe281474dada13911ee

src/qt/test/rpcnestedtests.cpp

@@ -14,17 +14,26 @@
 #include <QDir>
 #include <QtGlobal>
 
-static UniValue rpcNestedTest_rpc(const JSONRPCRequest& request)
+static RPCHelpMan rpcNestedTest_rpc()
 {
-    if (request.fHelp) {
-        return "help message";
-    }
-    return request.params.write(0, 0);
+    return RPCHelpMan{
+        "rpcNestedTest",
+        "echo the passed string(s)",
+        {
+            {"arg1", RPCArg::Type::STR, RPCArg::Optional::OMITTED, ""},
+            {"arg2", RPCArg::Type::STR, RPCArg::Optional::OMITTED, ""},
+            {"arg3", RPCArg::Type::STR, RPCArg::Optional::OMITTED, ""},
+        },
+        {},
+        RPCExamples{""},
+        [](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
+            return request.params.write(0, 0);
+        },
+    };
 }
 
-static const CRPCCommand vRPCCommands[] =
-{
-    { "test", "rpcNestedTest", &rpcNestedTest_rpc, {} },
+static const CRPCCommand vRPCCommands[] = {
+    {"test", "rpcNestedTest", &rpcNestedTest_rpc, {"arg1", "arg2", "arg3"}},
 };
 
 void RPCNestedTests::rpcNestedTests()