Add Options class to backup cli

What does this MR do and why?

This MR is part of the effort to decouple the gitlab-backup-cli gem from the gitlab rails code: #454906

This MR adds an Options class to the gitlab-backup-cli gem to set values based on options passed to the cli and their default values. This class will be used in the next MRs that add additional targets to backup: !164205 and !163584 (merged)

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

Numbered steps to set up and validate the change are strongly suggested.