FEATURE: Normalize the service worker route (PR #12343)


Not sure if I can approve most of my own changes, but this looks fine to me. The nginx changes are much more minimal and easy to understand this time around though.

@featheredtoast maybe we try this out on dev/meta next week, if safe after say 24 hours merge it in.

I know how scared we are of this change, but if we are going to do it, might as well do it now. Looks finished to me.