[mdns] add hidden API for public key
This commit adds support of registering a public key for a host/service.
This is required to enable Advertising Proxy feature for Thread devices.
For example:
```
NsdServiceInfo info = new NsdServiceInfo();
info.setServiceName("My Service");
info.setServiceType("_test._tcp");
info.setHostname("MyHost");
info.setHostAddresses(List.of(address1, address2));
info.setPublicKey(/* KEY RDATA */);
nsdManager.registerService(info, PROTOCOL_DNS_SD, listener);
```
Bug: 317946010
Change-Id: I367ebff8119d5c1dff0410c85e6fb86dca6c66b8
6 files changed
