Display newline changes in description diff

What does this MR do and why?

Replace newlines with ↵ in description diffs so that changes are visible in the diff.

For context, description diffs use diff-match-patch so the diffs are more compact and better suited to text diffs compared to the line-based diffs we do with code changes.

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

	Before	After
Adding a new line
Replacing new line with a space
Adding a new line with other text

How to set up and validate locally

1. Edit issue description with newline changes
2. View the diff using the link on the system note

Note: changes within 10 minutes of each other are merged into one diff

Related to #38094 (closed)