WIP Add MR description to discussion tab

• Move MR description to discussion tab
• Add You can also accept this merge request manually using the command line text to MR widget
  • This line makes much more sense within the MR widget rather than floating around by itself. I'm not sure if it's already like this in the new design
• Wrap branch names normally instead of break-all
• Move Download & Checkout buttons to their own line

Before	After

Discussion tab (description has the gray background):

Closes #25184 (closed)