MR Review panel: Create drawer to show pending draft comments from MR Review

Context

In the context of the wider effort to build an improved MR Review Panel as described in &14651 and #474794, this is step 1.

• Step 1: Review bar #525839 (closed))
• Step 2: New drawer to preview Review pending comments ⬅️ this issue
• Step 3-?: Iterate on improving drawer

Tasks

1. Button label "Finish review" changes to "Your review"
2. Add a numbered badge attached to the button to display the count of pending comments
3. When clicked, a drawer is shown
   • Fixed header area: Review submission form #525852
   • Scrollable area: List of pending comments
4. If summary comment is empty, then when drawer opens it should be in it's minimized state
   • When clicked, then it opens with the content editor. Note the current content editor for the summary comment is fine, the mockup of the toolbar is not exact to what is in production today.
   • The reason to do this is to leverage progressive disclosure of an optional field to minimize visual overload.
5. If summary comment is populated, then when the drawer opens it should be in it's expanded state

Taken from #525839 (closed)

1. If user is a reviewer, show the Review bar even if no pending comments exist yet
2. If "Your review" is displayed, then that is the primary button and "Code" becomes default secondary.

For more details of the review panel vs Pajamas drawer

Mockups

Figma

Button - With no pending comments	Button - With pending comments

Summary comment - Collapsed (Empty)	Summary comment - Expanded (Clicked on / populated)