reslove: Refactor DNS Answer to support 'until' in DnsAnswerItem

reslove: Refactor DNS Answer to support 'until' in DnsAnswerItem
Prepare for mDNS browse services to facilitate scheduled cache
maintenance queries when browsing for services.

Introduce dns_answer_add_full() and dns_answer_add_extend_full()
to explicitly handle the 'until' argument, enabling fine-grained control
over the time property of DNS answers.

Ensure backward compatibility while providing the flexibility to
specify 'until' for specific cases when needed

Co-authored-by: Vishwanath Chandapur <vishwanath.chandapur@philips.com>