Multilayer support when NAI requests are updated

Updates to ConnectivityService to support multilayer requests in any
flows which a NetworkAgentInfo has a NetworkRequest added/removed. This
would include both 'listen' and 'request' types of NetworkRequest
objects.

Bug: 174271773
Bug: 171991028
Test: atest FrameworksNetTests
atest NetworkStackTests
atest FrameworksNetIntegrationTests
atest NetworkStackIntegrationTests
atest CtsNetTestCasesLatestSdk

Change-Id: Iaff727e792828684e6ad4d07d0081e27992031be