Compile test hyperlight guests in CI

I was talking with @danbugs yesterday about our release process and how that affects the guests we publish. With hyperlight we try and be forward-compatible with guests by introducing deprecating features before removing them in a future version, but in practice it sounds like we don't always succeed in catching all issues.

One idea we were playing around with was to make `hyperlight-dev/hyperlight` run (compile) tests for guests. Or to have guests pull and try to build against hyperlight main in CI on e.g. nightly. Basically whichever yields the least amount of work and is most useful for guest maintainers.

More broadly I'd like us towards automating more of the release process, and I see this as part of that. The sooner we can catch compat issues or potential breakage, the better prepared we'll be for actual releases. @syntactically suggested maybe adding release branches in the mix here too, which might be a useful part of the solution. But I wanted to specifically file an issue about periodic compat testing before we get to other parts of automation.