In-memory host identity manager

This is a split of MCOL-6175. It covers only the in-memory prototype of the Host Address Manager.
It does not introduce persistent host IDs or modify any configuration files.
Instead, it focuses on:
• Creating a runtime-only abstraction for hostname/IP resolution inside CMAPI.
• Performing forward and reverse DNS lookups using a library that bypasses nsswitch and local aliases.
• Storing resolved results in memory
• Exposing a simple API for components to get normalized host identities.