Idea: scope_exit

[pfeatherstone]

This might be a nice PR:
https://godbolt.org/z/zocG4ejhs

The non-erased version is a lot better but there are use-cases for the erased version.
Also note, the erased version is slightly more efficient than using std::shared_ptr<void> with a custom deleter which calls exit function.

[davisking]

Nice, yeah, would be cool to have this kind of thing on hand. Have this tool at work and it's useful :)

[pfeatherstone]

Added #2875