Add one-off label migration doc to EP handbook page
What does this MR do
To add the one-off label migration instructions to the EP team handbook page for discoverability. This documentation build on top of the existing one-off policies doc, but I decided to add more details and examples, and make it visible in the EP team handbook so we can easily link to team members submitting these requests.
The MR also changes the MR template where the requests are usually originated from.
Edited by Jennifer Li