run workflow using solvers as a base image

[karmacoma-eth]

Example run:
https://github.com/a16z/halmos/actions/runs/9409762438

This works at least as a proof of concept. We should be able to optimize the 1min "build image step" a little bit more:

• since we want to keep the solvers package very minimal, we need to add the other dependencies we need in CI for halmos (git, python, foundry, etc)
• we need to checkout the current halmos from github and install it

It would be faster to use either an already published halmos:latest image (but wouldn't help for running tests on a branch).

Alternatively we could also publish an intermediary halmos-base image that already includes git, python, foundry, uv, etc. and we would only need to install the halmos checkout.

[karmacoma-eth]

(note: this PR does not yet enable publishing the halmos package, will do separately)

[daejunpark]

i ran again the test-ffi but it kept failing. do you have any idea?

[karmacoma-eth]

i ran again the test-ffi but it kept failing. do you have any idea?

weird, 404 trying to download foundry. Maybe now is a good time to switch test-ffi to the docker image too, since it doesn't rely on downloading the github release :)