Change RenderEngine::drawLayers to take a vector of LayerSettings pointers

Prework for the client composition cache logic which extends
LayerSettings. Passing in a set of pointers will reduce the
amount of copying needed when passing the LayerSettings to
RenderEngine.

Bug: 136561771
Test: atest librenderengine_test libcompositionengine_test
Test: atest VtsHalGraphicsComposerV2_2TargetTest
Test: go/wm-smoke

Change-Id: I0581be7762bf56cd7a3aab0511adf95cd6e2df76