Pacman: Add support for install reason

[Minei3oat]

SUMMARY

Pacman allows setting the install reason of packages. This PR adds this feature to the pacman module.

By default, no reason is explicitly set and the default behaviour of pacman is left untouched.

reason_for: all sets the install reason for all packages and represents the behavior of pacman when --asdeps or --asexplicit are specified.

reason_for: new; reason: dependency is a combination which is, as far as I know, not possible with pacman but very useful, as this enables specifying all wanted optional dependencies of a package without setting the already explicitly installed ones to dependency.

ISSUE TYPE

• Feature Pull Request

COMPONENT NAME

pacman

[ansibullbot]

cc @indrajitr @tchernomax
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[felixfontein]

Thanks for your contribution! Please note that you need to include a changelog fragment. I've included some first comments below.

[felixfontein]

CC @jraby

[github-actions]

Docs Build 📝

Thank you for contribution!✨

This PR has been merged and your docs changes will be incorporated when they are next published.

[jraby]

I agree with felix, we should try yo avoid calling pacman in a loop. (The module was just rewritten to avoid this).
I also think that no specifying the new parameter should simply let pacman do its default thing, without passing the value explicitly.

Thanks for your contribution!