Automation for dealing with backport.

[weinbe58]

Currently there is no automation in terms of backporting bug fixes and hence there have been multiple instances where bug fixes are backported to some release branches but not to others.

I think we need a more automated way of dealing with this going forward to avoid confusion.

[weinbe58]

One way we can do this is to have a workflow or a bot that monitors the tags and automatically opens up a PR that merges the change onto the release branches.

[kaihsin]

what would you think of? if this backport is to 0.17 how does workflow knows it can backport to 0.16 or 0.15 for example?