Merge bitcoin/bitcoin#22219: multiprocess: Start using init makeNode, makeChain, etc methods

e4709c7b56 Start using init makeNode, makeChain, etc methods (Russell Yanofsky)

Pull request description:

  Use `interfaces::Init::make*` methods instead of `interfaces::Make*` functions, so interfaces can be constructed differently in different executable without having to change any code. (So for example `bitcoin-gui` can make an `interfaces::Node` pointer that communicates with a `bitcoin-node` subprocess, while `bitcoin-qt` can make an `interfaces::Node` pointer that controls node code in the same process.)

  ---

  This PR is part of the [process separation project](https://github.com/bitcoin/bitcoin/projects/10). The commit was first part of larger PR #10102.

ACKs for top commit:
  jamesob:
    reACK e4709c7b56
  achow101:
    ACK e4709c7b56
  benthecarman:
    utACK e4709c7b56

Tree-SHA512: 580c1979dbb2ef444157c8e53041e70d15ddeee77e5cbdb34f70b6d228cc2d2fe3843825f172da84e506200c58f7e0932f7cd4c006bb5058c1f4e43259394834

src/rpc/misc.cpp

@@ -670,8 +670,9 @@ static RPCHelpMan echoipc()
         RPCExamples{HelpExampleCli("echo", "\"Hello world\"") +
                     HelpExampleRpc("echo", "\"Hello world\"")},
         [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue {
+            interfaces::Init& local_init = *EnsureAnyNodeContext(request.context).init;
             std::unique_ptr<interfaces::Echo> echo;
-            if (interfaces::Ipc* ipc = Assert(EnsureAnyNodeContext(request.context).init)->ipc()) {
+            if (interfaces::Ipc* ipc = local_init.ipc()) {
                 // Spawn a new bitcoin-node process and call makeEcho to get a
                 // client pointer to a interfaces::Echo instance running in
                 // that process. This is just for testing. A slightly more
@@ -689,7 +690,7 @@ static RPCHelpMan echoipc()
                 // interfaces::Echo object and return it so the `echoipc` RPC
                 // method will work, and the python test calling `echoipc`
                 // can expect the same result.
-                echo = interfaces::MakeEcho();
+                echo = local_init.makeEcho();
             }
             return echo->echo(request.params[0].get_str());
         },