Allow users to re-request a new review from a reviewer

What does this MR do?

Allows for users to re-request a new review from an assigned reviewer.

This allow for a flow of reviewing like:

• User A creates a merge request and request a review from user B
• User B reviews the merge request with the batch comments/review feature.
• User A pushes new changes, clicks re-request review
• User B gets a new todo to know they need to re-review the merge request.

Related to #293933 (closed)

Screenshots (strongly suggested)

(Screenshot not final UI - very rough to get idea working!)

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
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team