Switch to YAML based hosts file

Summary

Currently, we use the INI based hosts files for Ansible inventories. Switching to YAML would make them easier to be generated and verified. Also, it would be easier for scripts to read values from it (using e.g. yq) if necessary.

Use Cases

Proposal

Specification

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this section are to be interpreted as described in RFC 2119.