Refactor IpSecServiceConfiguration to Dependencies

IpSecService is going to be moved into ConnectivityService module,
so the hidden API usage should be removed.

NetdService.getNetdInstance is a hidden API, therefore the alternative
is to get the instance by Context.getSystemService.

Bug: 204153604
Test: FrameworksNetTests

Change-Id: I1bd8efc03c37654d12a8eadd3e78ed45e10b5691