Add CLI support to generate default config

[hu55a1n1]

Crate

ibc-relayer-cli

Summary

Add a CLI command to generate and output a config file with defaults.

Problem Definition

There is currently no way to create a default config file for hermes, so it would be nice to be able to generate a default config file that gives users a template to start with. In the future, we might also want to provide more config templates particularly for the tutorials in the hermes documentation and we could also provide a way to edit the config (maybe git style) using the CLI.

Proposal

We add the config command so that the interface is extensible to support future improvements such as config validation, etc. The generate subcommand could be interactive (based on the options it receives) to fill in parts of the default config template.

$ hermes config generate [options]
# prints the config to stdout

Acceptance Criteria

The config generate command must print a working config to stdout.

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For Admin Use

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[adizere]

Partly superseded by #2187. Prioritizing to next milestone, could be useful project for @Farhad-Shabani soon.

[romac]

This has been available for a while with the config auto command.