1991117 - Add option to copy a message tailored for backouts

Status: NEW

(Tree Management :: Perfherder, task)

Description

[Acasandrei Beatrice (needinfo me)]

Acceptance criteria

• Add a new template for replying to the backout comment on the culprit bug with improved and generic messaging (eg "detected changes following backout, no action needed", )
• Add ability to copy summary text via a button for changes detected following backout

Other suggestions for improved messaging that are not generic:

• "Good news - it looks like this patch will improve performance when relanded, because its backout was detected by our systems as a regression" - clear from the beginning whether it's something positive or negative
• "Note: The original landing from this bug appears to have improved performance, because its backout was detected by our systems as a regression"