ANDROID: rust: add security::binder_* methods

I haven't upstreamed these since I intended to add them as part of
sending binder itself upstream.

As an alternative, this code could live in Rust Binder itself. Though
this would require exporting the C versions of these functions.

Bug: 388786466
Change-Id: I42d1f8aa9563266f5ebba5565cb707f9a3e6df09
Signed-off-by: Alice Ryhl <aliceryhl@google.com>