Reproduce Repository X-Ray functionality - Introduce lock file classes

What does this MR do and why?

Context

In #474306 (comment 2025085630), we decided to migrate the Repository X-Ray functionality into the GitLab Rails monolith. This gives us two main benefits: (i) it will eventually allow us to run the service outside of the CI pipeline, and (ii) we can maintain the parsing logic centrally so that other domains can utilize it.

This MR

This MR is the first step in the migration progress. It introduces the LockFiles::Base class where the intention is for each lock file type to be represented by a child class. The RubyGems child class serves as an example of the implementation.

Next Steps: Eventually we will add all the languages/lock files currently supported in Repository X-Ray. Then we will introduce a lock file parser class that utilizes these LockFiles::Base child classes.

POC: For a more complete picture of the overall implementation, see: Draft: POC - Reproduce base functionality of Re... (!162125 - closed)

Resolves part of #476177.

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Related to #476177