Resolve "Design Comment: Edit Comment text"

What does this MR do?

This MR enables the possibility to edit discussion notes on Design.The user flow is pretty much the same we have on the Issue discussions:

• when user clicks Edit button, we open a textarea with note text;
• if user didn't add any changes and press Esc, we hide the textarea;
• if user added any changes, we show the confirmation modal about non-saved changes similarly to adding a new note;

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Issue #118609 (closed)