Adds option_will_fund info to the RPC listnodes output

[litch]

I'm having a lot of trouble with this. I have been able to get the code to run and return the values well, but I am unable to get the schema -> code-generation to create the files correctly.

From what I can tell, I should be able to make a change to the file changed:

doc/schemas/listnodes.schema.json

And that should bubble out first to .msggen.json. That is working correctly.

Then the contrib/msggen/msggen/__main__.py loads that file and should output a correct:

• cln-rpc/src/model.rs
• cln-grpc/proto/node.proto
• cln-grpc/src/server.rs
• cln-grpc/src/convert.rs

The included changes create new definitions for the ListnodesNodesOption_will_fund objects, however, they do not attach that object into the ListnodesNodes object.

I would appreciate any guidance here.