[binder_rs] Make Binder interfaces and Strong<> Sync

NDK Binder objects are thread-safe, so our Rust interfaces and Strong<>
objects can be marked as Sync.

Test: atest -p frameworks/native/libs/binder --include-subdirs
Bug: 164453341
Change-Id: I9aea4413cae14af136e1d6f5f4143cce30d65a37
diff --git a/libs/binder/rust/src/binder.rs b/libs/binder/rust/src/binder.rs
index 2a09afc..f79b1b7 100644
--- a/libs/binder/rust/src/binder.rs
+++ b/libs/binder/rust/src/binder.rs
@@ -50,7 +50,7 @@
 /// interfaces) must implement this trait.
 ///
 /// This is equivalent `IInterface` in C++.
-pub trait Interface: Send {
+pub trait Interface: Send + Sync {
     /// Convert this binder object into a generic [`SpIBinder`] reference.
     fn as_binder(&self) -> SpIBinder {
         panic!("This object was not a Binder object and cannot be converted into an SpIBinder.")