Add way to bulk promote environment variables

It would be good (within the compare view for instance) to be able to select all environment variables to promote. This would likely need some way to bulk select different groups (e.g. promote all, promote missing or promote changed).

Initial setup can be tedious if following common standard of using personal dev > dev > staging > prod as you have to manually promote each new variable (which can be a lot when first starting a new project).