*: Add presubmit script

Adds a `presubmit.sh` script to the repository root to automate
CI/CD checks. The script ensures code quality by running a series
of checks in the `rust/` directory.

Using `set -eux`, the script is configured to exit immediately if
any of the following steps fail:
 - Build the project with `cargo build`
 - Check code formatting with `cargo fmt -- --check`
 - Run the test suite with `cargo test`

Bug: b/439013538
Test: Ran the script locally
Change-Id: I0344c0e494bda49e0b09778f5cfdd0d3e4c01f26
Reviewed-on: https://bluetooth-review.googlesource.com/c/bluetooth/+/2700
Reviewed-by: Rob Mohr <mohrr@google.com>
Reviewed-by: Marie Janssen <jamuraa@google.com>