audioflinger: add effect creation probe mode

Add an argument to IAudioFlinger::createEffect() API to
ask AudioFlinger to just run the pre flight checks but not
create the actual audio effect instance and allocate resources.
This is the basis of an API for apps to query if a given
effect can be created without having to allocate the resources
and risk an exception when calling the constructor.

Bug: 150699608
Test: CTS and GTS Tests for audio effects
Change-Id: Ibdda22fd945c88c33e3c7342a7a5ed3e02d399ac