fix: generate help for recursive custom types - #1593

$ stellar contract invoke --source ee --network local --id custom-types -- recursive_enum --help

thread 'main' (2354011) has overflowed its stack
fatal runtime error: stack overflow, aborting

$ stellar contract invoke --source ee --network local --id custom-types -- recursive_enum --help

Usage Notes:
Each arg has a corresponding --<arg_name>-file-path which is a path to a file containing the corresponding JSON argument.
Note: The only types which aren't JSON are Bytes and BytesN, which are raw bytes

Usage: recursive_enum [OPTIONS]

Options:
      --recursive <List(Array<RecursiveEnum | Void>) | Void>
          Example:
            --recursive '{"List":[ {"List":[ {"List":[ RecursiveEnum ]}|"Void" ]}|"Void" ]}|"Void"'

  -h, --help
          Print help (see a summary with '-h')