Update batch comments to match new discussion design

The batch comments design is broken. Let's update it to match the new discussion design.

Essentially we just need to move everything into the container.

Design

For reference, here's the current state:

master	GitLab.com

Original description

The following discussion from !8331 (merged) should be addressed:

• @mikegreiling started a discussion: (+2 comments)

  @annabeldunstone it looks like we did not anticipate the multi-comment drafts feature in this redesign. It caused quite a few merge conflicts that I just needed to wade through and the result looks less than stellar:

  

  I've updated the CSS within draft_note.scss to make it look less broken:

  

  But as there are no design guidelines for this, I want to make sure you have another look at it.

/cc @fatihacet