Add command to dump network config settings in XDR-JSON format

[leighmcculloch]

trafficstars

What problem does your feature solve?

Sometimes we need to get the Soroban config settings for the network.

What would you like to see?

A subcommand on the stellar-cli that collects the config settings for the network and outputs them as a JSON file, consistent with the files stored here:

• https://github.com/stellar/quickstart/tree/main/local/core/etc/config-settings/p23

What alternatives are there?

Stellar-core serves the config via a url on it's admin http endpoint, we will continue to use that as well in some situations, but it would be helpful if the cli offered on its own a way to get all the configs.