Multilayer request updates to request callbacks

Updated to ConnectivityService to support multilayer requests when
sending request level callbacks.

Bug: 174797702
Bug: 171991028
Test: atest FrameworksNetTests
atest NetworkStackTests
atest FrameworksNetIntegrationTests
atest NetworkStackIntegrationTests
atest CtsNetTestCasesLatestSdk

Change-Id: I3d6896f5705509bcfff5544d2eb13c31feaf1937