Adding per-app support for app add/remove

Adding support for per-app network functionality to react to application
installs, removals and updates. Also, opportunistic cleanup of a couple
annotations.

Bug: 177092163
Bug: 176494815
Test: atest FrameworksNetTests
atest NetworkStackTests
atest FrameworksNetIntegrationTests
atest NetworkStackIntegrationTests
atest CtsNetTestCasesLatestSdk

Change-Id: I45acbd0d2ef50d575f14a944ce82b185ed69f219