lights: Re-write example service in Rust

Add a re-implementation of the Lights HAL example service in Rust. This
was originally written as the start of a Cuttlefish specific
implementation of this service, but it's simple / small enough that
replacing the current Android C++ one with it shouldn't bring in any
trouble while providing yet another Rust service example to the tree.

Tested: built VtsHalLightTargetTest and ran in Cuttlefish
Bug: 286106270
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:a796fb113c405838424e61fd0b4cd6e0ef86c5a7)

Change-Id: I01eaf9ce7c6086e1429f52ff4f7f92cebc5360b6