When submitting a non-batch comment also submit a review with comment unless user opts out

Context

Despite our focus on improving the visibility and usage of the Review feature, there are still some use-cases that lead to reviewers sometimes forgetting to submitting the Review back to the author.

Namely, when adding a single comment it's fairly easy to use the "Add a comment now" and miss the updating of the Review state altogether.

Moreover, when the Review has an outdated state, this can lead to mismatched expectations when it comes to the Action focused merge request homepage (&13448).

Thus, it would be beneficial to link the user flow of adding a comment now with the updating of the Review state.

Current flow of adding a single comment

flowchart TD
    A[Reviewer] --> B(Add to Review)
    C(Add a comment now)
    A --> C
    B --> D(Publish review)
    D --> E("Comment(s) published")
    C --> E

Proposal

Make the "Add a comment now" be linked with publishing a review with "Comment".

If the comment includes a quick action to /submit_review then the default behaviour os overriden.

Proposed new flow

flowchart TD
    A[Reviewer] --> B(Add to Review)
    C(Add a comment now)
    A --> C
    B --> D(Publish review)
    D --> E("Comment(s) published")
    C -->|Submit review with comment| E

The action of submiting the review is automatically achieved yet control should be given on the UI.

Checkbox should only show in these conditions:

• I am a reviewer
• has been asked to review
• haven't submitted my review yet

Checkbox should be default enabled if:

• A review has not been started (disappears upon addition

The check would be analogous to having /submit_review comment in the comment. If it's saved as draft, it's saved as such and only execute upon Review publishing.

UI brainstorming/proposal

Text should probably say something like: "Submit my review upon publishing of this comment"

Questions to explore

• Could we use keyboard shortcuts to help make the review submit flow more natural without a mouse?