Refactor Dependency List Vuex store

What does this MR do?

This is part of the work to implement the display of Dependency Scanning results in the Dependency List.

The bulk of this is simply moving the existing Vuex store to a reusable module. The purpose of this is to facilitate adding a second instance of the module, so that there can be two independent dependency lists at once, as specified in the feature's issue.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation created/updated or follow-up review issue created
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content
• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.