Convert IEffect and IEffectClient to AIDL

This change replaces the manually-parceled IEffect and IEffectClient
with AIDL definitions.

In addition, this includes a small library that facilitates shared
memory regions over AIDL.

Bug: 160253486
Test: Ran effects-related CTS tests. Manual verification of basic
      audio functionality on Sargo.

Change-Id: I5a9c5f2f24c10072ad5067acc71aa30581af41c1