Proof-of-concept Rust wrapper

This contains Rust wrappers around enough of the Python API to implement Rust versions of the `battery_client` and `run_scanner` examples. The goal is to gather feedback on the approach, and of course to show that it is possible.

The module structure mirrors that of the Python. The Rust API is not optimally Rust-y, but given the constraints of everything having to delegate to Python, it's at least usable.

Notably, this does not yet solve the packaging problem: users must have an appropriate virtualenv, libpython, etc. [PyOxidizer](https://github.com/indygreg/PyOxidizer) may be a viable path there.

rust/README.md

@@ -0,0 +1,42 @@
+# What is this?
+
+Rust wrappers around the [Bumble](https://github.com/google/bumble) Python API.
+
+Method calls are mapped to the equivalent Python, and return types adapted where
+relevant.
+
+See the `examples` directory for usage.
+
+# Usage
+
+Set up a virtualenv for Bumble, or otherwise have an isolated Python environment
+fur Bumble and its dependencies.
+
+Due to Python being
+[picky about how its sys path is set up](https://github.com/PyO3/pyo3/issues/1741,
+it's necessary to explicitly point to the virtualenv's `site-packages`. Use
+suitable virtualenv paths as appropriate for your OS, as seen here running
+the `battery_client` example:
+
+```
+PYTHONPATH=..:~/.virtualenvs/bumble/lib/python3.10/site-packages/ \
+    cargo run --example battery_client -- \
+    --transport android-netsim --target-addr F0:F1:F2:F3:F4:F5
+```
+
+Run the corresponding `battery_server` Python example, and launch an emulator in
+Android Studio (currently, Canary is required) to run netsim.
+
+# Development
+
+Run the tests:
+
+```
+PYTHONPATH=.. cargo test
+```
+
+Check lints:
+
+```
+cargo clippy --all-targets
+```