Implement proper subtype advertising

Implement subtype advertising by advertising an additional PTR record if
subtype advertising was requested.

For an advertiser a subtype is just an additional PTR record, so this
just involves plumbing the subtype down to MdnsRecordRepository, which
includes the additional record in the service registration.

Bug: 266167702
Test: atest
(cherry picked from https://android-review.googlesource.com/q/commit:ce44beb7aa3d17dabab5e596a1b27cb9422e076e)
Merged-In: I09e780af25149162f16bd75410ddc50f160a0dab
Change-Id: I09e780af25149162f16bd75410ddc50f160a0dab
8 files changed