Add "reviewed but not approved" state in merge request sidebar

What does this MR do and why?

• Aligns all checkmarks and re-review buttons
• Adds explicit state "This has been reviewed but not approved yet"
• Removes success checkmark (appears when you click re-request review)

Screenshots or screen recordings

Before	After

How to set up and validate locally

Find an MR, or impersonate users to get to the following approval states:

• Approve
• Approve with review (submit an actual review and approve)
• Review without approval
• Assigned reviewer without approval or review

#394879 (closed)