Add trait implementations for Rust binder crate

Implements Error for StatusCode in the bindgen generated bindings, which
makes usage simpler. Implements Eq for SpIBinder. Exposes a method to
promote weak binder references to strong ones.

Bug: 161559357
Test: m libbinder_rs
Change-Id: Ia2f891c2f0f84ed0454039169ed42ab20401c1a4
6 files changed