Updater library

This is the C/Rust side of the Shorebird code push system. This is built in Rust with a C API for easy calling from other languages, most notably for linking into libflutter.so.

See cli/README.md for more documentation on the library.

Parts

• cli: Test the updater library via the Rust API (for development).
• dart_cli: Test ffi wrapping of updater library.
• library: The rust library that does the actual update work.