Geo: Generalize replicables route, controller, view, and index.js

What does this MR do?

This is a refactor to ensure that when adding new replicables, we do not need to touch any of this code.

To do

• Generalize tests

Closes #219315 (closed)

Screenshots

No visual change.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry => no change in behavior
• [-] Documentation (if required) => I will open a follow up MR to update https://docs.gitlab.com/ee/development/geo/framework.html#blob-replicator-strategy, which is a developer doc in alpha anyway
• Code review guidelines
• [-] Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.