Generate a query packet with MdnsPacket

This is a no-op change, only refactoring the query packet
generation code to use MdnsPacket. This refactoring enables the
insertion of additional sections into the query packet and
facilitates the determination of truncation requirements.

Bug: 312657709
Test: atest FrameworksNetTests NsdManagerTest
Change-Id: I3671842b6d433e1856a1efae643f3fe1f6c532d1