Allow a way to track the active request in an NRI

As we are now allowing for multi-layered requests in NetworkRequestInfo
(NRI), we need a way to track which of those requests ended up being
satisfied. This also includes updates to NetworkRequestInfo itself to
support multilayared requests.

Bug: 173146509
Bug: 171991028
Test: atest FrameworksNetTests
atest FrameworksNetIntegrationTests
atest CtsNetTestCasesLatestSdk
Change-Id: I7bb5a564769c90928871fe28de05195c9cfae6b5

Change-Id: Ibf37f94b53eb2e833821553e00d76fe38bfea266