Refactor the delete branch and delete protected branches from HAML to vuejs

Currently in our Repository -> Branches view, the current HAML implementation is blocking this particular MR

I propose changing the implementation from HAML to Vuejs as part of our current efforts to make all of our modals consistent across GitLab.

Discussed this with Winnie here and while there's no consensus it seems reasonable to do this if it blocks the new implementation of the modals