Merge bitcoin/bitcoin#21897: rpc: adjust incorrect RPCHelpMan types

<pre>Merge bitcoin/bitcoin#21897: rpc: adjust incorrect RPCHelpMan types 7031721f2cc3eef30c46ff50c52328e9ba8090e0 rpc/listaddressgroupings: redefine inner-most array as ARR_FIXED (Karl-Johan Alm) 8500f7bf54d3e27fd2fa7fda15ad833f5688c331 rpc/createrawtransaction: redefine addresses as OBJ_USER_KEYS (Karl-Johan Alm) d9e2183c50f50465b9f173171fee240949bf8bd2 rpc: include OBJ_USER_KEY in RPCArg constructor checks (Karl-Johan Alm) Pull request description: This PR adjusts the two issues I encountered while developing a tool that converts RPCHelpMan objects into bindings for other language(s). The first is in createrawtransaction, where the address part, e.g. bc1qabc in &gt; createrawtransaction '[]' '[{"bc1qabc": 1.0}]' is declared as a `Type::OBJ`, when in reality it should be a `Type::OBJ_USER_KEYS`, defined as such: https://github.com/bitcoin/bitcoin/blob/5925f1e652768a9502831b9ccf78d16cf3c37d29/src/rpc/util.h#L126 (coincidentally, this is the first and only (afaict) usage of this `RPCArg::Type`). The second is in the `listaddressgroupings` RPC, which returns an array of arrays of arrays, where the innermost one is a tuple-thingie with an optional 3rd item; this is an `ARR_FIXED`, not an `ARR`. ACKs for top commit: MarcoFalke: ACK 7031721f2cc3eef30c46ff50c52328e9ba8090e0 &#128000; Tree-SHA512: 769377416c6226d1738a956fb685498e009f9e7eb2d45bc679b81c5364b9520fdbcb49392c937ab45598aa0d33589e8e6a59ccc101cf8d8e7dfdafd58d4eefd0</pre>