Create RPM package class

What does this MR do and why?

Extract the RPM Repository package format related code from Packages::Package to Packages::Rpm::Package and update all related files like services, finders accordingly.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

The RPM Repository isn't available for customers yet, and we have no RPM packages on gitlab.com.

Thus, we can just be sure that the specs are green since there are no customer facing changes involved in the refactor.

Related to #435835 (closed)