Cleanup config

xchain config should probably have more high level sections
client
aggregator
buffer

Its maybe nicer to put it in TOML if the deploy script can bear writing to it. IDK I'll probably keep in JSON and just have high level map breaking things down. Other option is ~/.xchain/{client-config.json aggregator-config.json buffer-config.json}

Start by locating the xchain configuration and the deploy script mentioned in the issue. Compare the proposed high-level client, aggregator, and buffer sections with the current JSON layout; done means the configuration structure and chosen file organization are agreed and updated without breaking deployment.

Written by the indexing model from the issue text.