feat: ✨ Allow specifying when to run a scope guard

[ion098]

Allows running a scope guard only when the scope is (or is not) exited due to an exception

[ricab]

Thank you @ion098, this is good stuff. In my view, this would be useful mainly in places where there are multiple return paths (in other cases, one might as well just call the function or dismiss the guard directly before returning). However, I have little time to tend to CI these days and I don't want to merge before that.

It would be premature to address them now but, as an advance notice, before merging I would have some requests, relating to commit organization, test coverage, and documentation.

I will leave this open for now, so that it is visible to anyone interested. Hopefully I will find some time to update things eventually.

[ricab]

Hey @ion098, it looks like some declarations need matching updates: https://github.com/ricab/scope_guard/actions/runs/10817232638/job/30144354061?pr=33#step:8:14

And other runs you setup don't work.

Thanks again for your interest.