resolv_integration_test: Test message compression

Per RFC 1035 section 4.1.4, the domain name could be preseneted as
either:
- a sequence of labels ending in a zero octet
- a pointer
- a sequence of labels ending with a pointer

The first presentation has been verified in existing test cases.
This commit verifies the remaining presentation which uses a pointer.

Test: cd packages/modules/DnsResolver && atest
Change-Id: I705a3f5c96920cc0431aae4f8537db07e280bd1b