Delete the clatd functions from NetworkManagementService.

Make Nat464Xlat talk to netd directly instead of through
NetworkManagementService. The methods in NetworkmanagementService
don't really provide any value: since the only thing they do is
call into netd, we might as well have the callers talk to netd
directly,

In order to do this, pass INetworkManagementService and INetd to
the NetworkAgentInfo constructor, and update callers appropriately.

Bug: 65674744
Test: builds, boots
Test: atest FrameworksNetTests
Change-Id: Iac4cfe709c6279e4d9682b6754963e533707bd12