[KA02.5] Use binder thread and executor to invoke callback

Currently, client side of keepalive event handling rely on a
newly created thread, looper, messenger and handler per object.

However, by creating oneway AIDL interface with the executor,
the callbacks can be invoked on the binder thread with user
specified context, which not only greatly simplify the design
but also reduce the cost of current thread modeling.

Bug: 114151147
Bug: 123969871
Test: 1. atest FrameworksNetTests --generate-new-metric 10
      2. atest-deflake.sh

Change-Id: I27504074cd28d5b5eb94a7ec0e97ebaaaaa1ae3d