Add service type clients to servicediscovery dumpsys

Add service type clients, and their listener counts to
servicediscovery dumpsys. This information will help identify
currently discovered services and monitor for client leaks.

Sample output:
DiscoveryManager:

  ServiceTypeClient: Type{_nmt079019787._tcp.local} \
      SocketKey{ network=116 interfaceIndex=68 } with 1 \
      listeners.
  ServiceTypeClient: Type{_nmt079019787._tcp.local} \
      SocketKey{ network=115 interfaceIndex=67 } with 1 \
      listeners.
  ServiceTypeClient: Type{_nmt079019787._tcp.local} \
      SocketKey{ network=100 interfaceIndex=47 } with 1 \
      listeners.

Bug: 324156009
Test: dumpsys servicediscovery
Change-Id: Idde31b9aabd6194c3f92e72c2345cbdd33f4b0fd