[Feature sync] Propagate network interface index to MdnsServiceInfo

For Matter, in addition to the InetAddress and port, we also need
to know the associated NetworkInterface index. With this change,
the interface index is propagated from the MdnsSocketTypeClient
through to MdnsServiceInfo based on a flag (defaulting to -1 for
unspecified, if the flag is disabled).

Validated end-to-end against a commissioned Matter device,
enabling the flags, verifying the returned network index against
an adb shell 'ip link show' output.

Bug: 254155029
Test: atest FrameworksNetTests
Change-Id: I96e804b32cdeeff3ed22da35a030df4d5dbb179a