rust: add more bisection scripts, documentation

This CL adds scripts that make the following tasks easier:
- setting a ChromeOS checkout up for Rust bisection
- writing the script invoked by `git bisect run`

It also adds documentation describing how all of this fits together.

BUG=b:236746843
TEST=TODO

Change-Id: Ifa8c2826f3b048fdfb06443db9f4e1ea3a1ead57
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/overlays/chromiumos-overlay/+/3733996
Reviewed-by: George Burgess <gbiv@chromium.org>
Tested-by: George Burgess <gbiv@chromium.org>
Reviewed-by: Michael Benfield <mbenfield@google.com>
4 files changed