Fix comment on image discussion icon alignment (update icons)

What does this MR do?

EE MR, https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/3683

• Fix comment on image discussion icon alignment by moving to whole SVG icon (SVG now includes blue dot and comment icon)
• Fix blurriness on non-retina screens

Before	After

Are there points in the code the reviewer needs to double check?

I tried re-using the sprited SVGs for the CSS cursor but x:link just doesn't work in a data URI SVG in CSS.

$sprite-path: image-path('icons.svg#image-comment-dark');
cursor: url('data:image/svg+xml;utf8,<svg xmlns="http://www.w3.org/2000/svg" width="24" height="24"><use xlink:href="#{$sprite-path}" /></svg>')
  $image-comment-cursor-left-offset $image-comment-cursor-top-offset, auto;

So we need to duplicate the cursor icons into gitlab-svgs/illustrations which are standalone and have an explicit dimensions.

Why was this MR needed?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

Todo

• Update gitlab-svgs dependency
  • Merge gitlab-svgs!36 (merged)
  • Wait for npm release, https://gitlab.slack.com/archives/C0GQHHPGW/p1512547783000075

What are the relevant issue numbers?

Closes #39608 (closed)