Name specific app for rapid data usage.

When a single app is responsible for more than half of the data usage
that caused us to trigger a "rapid usage" alert, name that app in the
notification.  Tests to verify.

Move NPMS->NSS direct calls to "Internal" pattern, following
best-practices to avoid unnecessary AIDL exposure.

Remove 3G/4G split mobile plan support, which has been deprecated for
years and was never supported in a shipping product.

Move MultipathPolicyTracker in tree to reflect its package name.

Test: bit FrameworksNetTests:*
Test: bit FrameworksServicesTests:com.android.server.NetworkPolicyManagerServiceTest
Bug: 69263587, 64221505, 73431080, 72746951
Exempt-From-Owner-Approval: approved in previous PS
Change-Id: I3e4ec1ae2222d51b232f76f32faca93d4f8cd272