Merge changes I6f6853a3,I2c6234a1,Iad51c4cf,Ib5e658df,Ia6f0df08, ...

* changes:
  SF: Define mock::EventThread
  SF: Separate EventThread into interface and impl
  SF: Define mock::RE::RenderEngine et al
  SF: Separate RenderEngine into interface and impl
  SF: Define Hwc2::mock::Composer
  SF: Separate Hwc2::Composer into interface and impl