Replace existing renamed diff viewer FSM with global GitLab FSM

What does this MR do?

Replaces an existing FSM with the RFC#65 FSM implementation.

The basic changes here are:

• Move the constants from a global diffs constants file into the more specific diff_viewers constants file
• Create a file just for the Renamed Diff Viewer State Machine
• Remove the state tests from the component and test the new Renamed-Diff-Viewer-specific state machine
• Update the component to have a state machine attached instead of ad hoc is and transition methods

Roadmap

Right now, the GitLab product contains a base finite state machine implementation that is unused.

I know of two ad hoc implementations of finite state machines in the codebase, and this is one of the MRs I had opened (a long time ago) to update them.
Since the past MRs were closed for lack of availability, this is a re-opened (rebase, tweaked, etc.) version of the original MR.

MR	Notes
!32365 (merged)	Implement a basic Finite State Machine (that intentionally emulates xstate/fsm in many regards)
!37285 (closed)	Update Cluster FSM
We're here 👉🏻	Update Renamed Diff Viewer FSM

Screenshots

N/A, all ~"feature::maintenance"

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.
• Tested in all supported browsers