networkstack aidl: use versions for imports

This makes sure that when developers add a new version of an interface,
or when interfaces are being frozen, the runtime/buildtime situation of
clients depending on those interfaces remains the same. This is required
for AIDL to continue working at scale.

Bug: 188871598
Test: build
Change-Id: I564605ac7f62a8f5b64d540f4cb310336954acff