Adds an overview document with a proposed plan and test bed architecture
for e2e testing the clients.
Drivers are available for [each platform using
Appium](https://appium.io/docs/en/2.3/ecosystem/drivers/).
- Update CI to run on our self-hosted M1 runner as well (macos-14)
- Sanitize build environment in `build-rust.sh` to keep only needed ENV
vars from Xcode
- Build both `x86_64` and `aarch64` targets with a single `cargo build`
instead of a loop
- Store artifacts in ephemeral locations
Fixes#2329
