Add mDNS service instance name parser.

This will be used for parsing user-provided names to 'adb connect' and
'adb pair' in order to check for matches in the mdns service registry.

Bug: 152886765

Test: $ANDROID_HOST_OUT/nativetest64/adb_test/adb_test
--gtest_filter=mdns_utils*

Change-Id: Ifd74b4394212853c1c193a2ea64937f6a6a0ff24