Create MdnsServiceTypeClient per network

The running task in MdnsServiceTypeClient would be cancel if the
requests using other networks for the same service type start a
new discovery. Besides, the instanceNameToResponse cache would
be incorrect too. The service attributes may be different on
different networks, so there needs to be a different instance
of the cache. Thus, the MdnsServiceTypeClient needs to be
Network-specific.

Bug: 265787401
Test: atest FrameworksNetTests
Change-Id: Id5ac42f3522a774fe9789c0de4d5357501b63868