Change layout of external services page to increase configuration button action usage

Created by: ryan-blunden

Based upon usability testing for adding a new external service, something needs to be done with the quick configuration buttons as both participants missed them and didn't see them until explicitly pointed out.

I've created a reworked mock of the GitHub external services configuration page which moves the buttons to the left-hand side of the editor while also moving the help text about using the monaco editor to the top.