Resolve "Links to discussions on the merge request diff don't expand the discussion"

What does this MR do?

• Fixed the bug of discussion links on MR diffs not expanding the discussion when clicked.
• Add support for expanding discussions if the anchor is for a note, a discussion, or a line of code.
• Update spec/helper/vuex_action_helper to support actions that use getters.

Screenshots

What are the relevant issue numbers?

Closes #48169 (closed)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides