Add 3-segment format for gl_repository

What does this MR do?

Implements #215315 (closed), a new gl_repository format:
[repository holder class]-[repository holder id]-[repository type], where:

• repository holder class would be the active record class name (e.g. "project")
• repository holder id would be the active record id (e.g. 7)
• repository type indicates it being code, wiki or design.

So project 7's wiki could be represented as project-7-wiki.

Backward compatibility is implemented so the old 2-segment format would still work.

The IdentifierParser is extracted as its own object, because I find we repeatedly do split at different places, and wrapping this as object helps caching this result.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• Documentation (if required)
• 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.