Merge #16240: JSONRPCRequest-aware RPCHelpMan

b6fb617 rpc: switch to using RPCHelpMan.Check() (Karl-Johan Alm)
c7a9fc2 Make the RPCHelpMan aware of JSONRPCRequest and add Check() helper (Karl-Johan Alm)
5c5e32b rpc: migrate JSONRPCRequest functionality into request.cpp (Karl-Johan Alm)
0ab8ba1 rpc: fix RPC help requirements for getblocktemplate (Karl-Johan Alm)

Pull request description:

  Every single RPC call has a helper-section at the start, which throws a help string if the user asks for help or if the user provided too few/many arguments.

  ```C++
  const RPCHelpMan help{...};
  if (request.fHelp || !help.IsValidNumArgs(request.params.size())) {
      throw std::runtime_error(help.ToString());
  }
  ```

  or (older version)

  ```C++
  if (request.fHelp || request.params.size() < min || request.params.size() > max)
      throw std::runtime_error(
          RPCHelpMan{...}.ToString()
      );
  ```

  It seems like an obvious improvement, and less copy-pasting, to make `RPCHelpMan` aware of `JSONRPCRequest`, and to let it handle the checks instead. Both of the above become

  ```C++
  RPCHelpMan{...}.Check(request);
  ```

  which means we save roughly 3 lines per RPC command, and the `RPCHelpMan` instance is never referenced afterwards, so the approach is a tiny fraction cleaner.

  This is a complete update, sans a few special case locations that had special rules. 623 lines turn into 284 (which includes the addition to `RPCHelpMan`).

ACKs for top commit:
  laanwj:
    code rview and lightly tested ACK b6fb617
  MarcoFalke:
    ACK b6fb617, looked at the diff, verified move-only where applicable

Tree-SHA512: eb73f47f812512905b852e313281d1c8df803db40a6188aa39d5a7586631664db6764491152a8a96769946c796dc56d38c6e3a66ddd06ba3fb9d20050e6274e1

Author: MarcoFalke

src/Makefile.am

@@ -175,9 +175,10 @@ BITCOIN_CORE_H = \
   rpc/blockchain.h \
   rpc/client.h \
   rpc/protocol.h \
-  rpc/server.h \
   rpc/rawtransaction_util.h \
   rpc/register.h \
+  rpc/request.h \
+  rpc/server.h \
   rpc/util.h \
   scheduler.h \
   script/descriptor.h \
@@ -481,7 +482,7 @@ libbitcoin_util_a_SOURCES = \
   interfaces/handler.cpp \
   logging.cpp \
   random.cpp \
-  rpc/protocol.cpp \
+  rpc/request.cpp \
   support/cleanse.cpp \
   sync.cpp \
   threadinterrupt.cpp \

src/bitcoin-cli.cpp

@@ -12,6 +12,7 @@
 #include <fs.h>
 #include <rpc/client.h>
 #include <rpc/protocol.h>
+#include <rpc/request.h>
 #include <util/system.h>
 #include <util/strencodings.h>
 

src/rest.cpp

@@ -12,6 +12,7 @@
 #include <primitives/block.h>
 #include <primitives/transaction.h>
 #include <rpc/blockchain.h>
+#include <rpc/protocol.h>
 #include <rpc/server.h>
 #include <streams.h>
 #include <sync.h>