Support for Windows and macOS runners

[AnimMouse]

As composite-based actions now has support for conditionals, we can now run a separate script that runs on Windows and macOS to maximize available disk space.

[easimon]

The action is quite specific on Linux and depends on the concrete VM types and available mounts -- it also abuses the fact, that the disks (amount and sizes) are not exactly as specified here. Also, the action uses Linux LVM to create virtual volumes on top of files -- something that is not directly translatable to Windows or MacOS, and something I do not know an equivalent for on these OSes.

That being said, I am open for pull requests to support that.

[reitermarkus]

For macOS, I have a step in my dotfiles repo which removes (or at least tries to) remove all preinstalled software. In my case it's more about having a clean slate rather than maximizing space, which is why I'm simply mving most things since rming would take considerably longer.