Use hidl.allocator for IAllocator.

android.hidl.memory is being split into android.hidl.memory and
android.hidl.allocator since the former is a passthrough hal and the
latter is a binderized service.

Bug: 35327976
Test: hidl_test, lshal, youtube/camera works
Change-Id: I7a2e72dcd3721d2689eb7ef95f5b140ecc1c446f