fa483e13b3 rpc: Add RPCHelpMan for machine-generated help (MarcoFalke)
fa0d36f712 rpc: Include rpc/util.h where needed for RPCHelpMan (MarcoFalke)
Pull request description:
This introduces a manager for the RPC help generation and demonstrates its use of it in some RPCs.
It is the first non-exhaustive step toward #14378 and I will create pull requests for the next steps after this one is merged.
Tree-SHA512: 86f68322443ff01cd964aaf0ebe186be63fbebe4c47676cf7a622cc2b5305fd176bd57badfd1bbf788a036812253eb0dead74ecc3b30664c3e0d9392b2248054