[Thread] support resolving a host for NsdPublisher

This CL lets NsdPublisher support resolving an mDNS host via one-shot
mDNS query. Because NsdManager not yet responds to such a query
properly, we cannot add an integration test for this. I've verified the
Discovery Proxy use case work properly on real devices.

Bug: 322434640
Test: atest NsdPublisherTest

Change-Id: Ie67f2fb9dd012408c123c354fc29f1a943280780
3 files changed