Add mdns files and unit tests

- Put mdns code to service/mdns because we don't want to impact
  coverage for code that's not yet in use.
- Also fix some lint errors
  - Common typo errors
  - Lines longer than 100 characters
- Update IgnoreUpTo from S to SC_V2 because the tests should be
  ignored until T.

Bug: 232766079
Test: atest FrameworksNetTests
Change-Id: I19af3bf7ae004bd37960f2ad9014cf0c6a804c8d
38 files changed