[rust] Test chrome://crash/rust

This trivially tests that the debug URL chrome://crash/rust does indeed
crash Chrome.

Although trivial, this Rust crashing code will be the first bytes of
Rust to run on our test infrastructure, so if there are any unexpected
runtime issues from using Rust in our CI then we should find them.
(Unless of course a crash is indistinguishable from the intentional
crash here, but it's a start).

Bug: 1368726
Change-Id: I715c7ba5946e6464de758f0dfed50176b78f625c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4588749


Reviewed-by: Alexei Svitkine <asvitkine@chromium.org>
Commit-Queue: Adrian Taylor <adetaylor@chromium.org>
Reviewed-by: danakj <danakj@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1153881}