Executors instead of Handlers; collections.

New API council guidance is to have developers provide an Executor
instead of a Handler for specifying where a callback should be
dispatched.

Recommend that raw arrays be switched to Collections<> instead.

Disable overload checking, since it's far too noisy.

Test: sanity-checked linter output
Bug: 37893784, 34192159
Change-Id: Ifc9a69bfed1a1004c6604e12987a606d1d3fd6af