Many applications use ConnectivityManager without needing
TetheringManager (or without calling legacy ConnectivityManager methods
that delegate to TetheringManager), so initializing TetheringManager
when ConnectivityManager is created wastes resources.
This is especially true considering that TetheringManager is not trivial
to initialize (worst case scenario it starts a thread and does multiple
Binder requests), and ConnectivityManager is created in ActivityThread
when setting up the app proxy on startup.
Bug: 190556328
Test: atest FrameworksNetTests CtsNetTestCases TetheringTests
Change-Id: I2ba7b8f2b9e1c934cfb082776b8d643f2f2c17e5
e4d1cd970e