luet install could do with a --cleanup flag

[Itxaka]

Is your feature request related to a problem? Please describe.
when installing packages and using --system-target luet will use that dir as a root dir to install the package structure on there.
unfortunately it will also use that dir to store all the temp stuff under TARGET/var
That means that if you are installing some artifacts to a given specific dir, you will end up with extra files in there

Describe the solution you'd like

the install to have a --cleanup flag that would indicate luet to FULLY remove all temp dirs used during that run.
Only opt-in as it modified existing behaviour and sometimes the cache can be useful if you install more than one artifact into the same dir, otherwise it will need to refresh the repos and everything on each install.

Describe alternatives you've considered

manually removing those dirs after

Additional context