add a3-rust workflow to generate verification output from Halley Young's Rust checker

[NikolajBjorner]

This is going to be my first attempt to integrate what I call the a3-rust checker with a github project.
There are two parts to it:

1. a3-rust.yml - a standard github action workflow that calls an extended static checker for rust to identify common programming mistakes.
2. setting up agentic workflows in the repository and installing an agentic workflow.

   • per gh.io/gh-aw (https://github.github.io/gh-aw/setup/quick-start/)

     • open a fresh code space in github.
     • gh extension install github/gh-aw
     • and I tend to then "gh aw init" and "git push" though the setup instructions are fluctuating a bit.
     • agentic workflows are soon going to be broadly advertised. So you are still cutting edge.
     • then, also from the litebox repository do: "aw add https://github.com/Z3Prover/z3/blob/master/a3/a3-rust.md" It should install the agentic workflow I prepared to post-process the output of a3-rust.yml.

     The two workflows are set up to be run manually. You can change this, but first run a3-rust.yml, then when it finishes (take 1hr currently), then run the agentic workflow.

It should create an issue, hopefully with a reasonable report if it claims it finds bugs. I haven't been able to test this last mile step because I can't post issues from my sandbox (or at least I don't easily see how to do this).

Could I persuade you to give it a spin?

@microsoft/halleyyoung_microsoft
@ Peli