Use feature_configs/feature_values in nimbus-ui

[jaredlockhart]

Let's migrate the nimbus-ui over from feature_config to using the new feature_configs field added in https://github.com/mozilla/experimenter/issues/6739. This ticket won't modify the UI itself so users will still only be able to select a single feature but it'll be sent as an array. We can update the UI itself as a followup.

┆Issue is synchronized with this Jira Task

[lmorchard]

I've got a rough start on UI tweaks to support multiple features in branches over here:

https://github.com/mozilla/experimenter/compare/6740-multifeature-ui?expand=1

Likely I won't quite finish it before I have to wipe my laptop tomorrow, so hopefully it'll be a good starting point to pick up from 😅

[jaredlockhart]

Thank you @lmorchard , a true mensch till the bitter end ❤️

[data-sync-user]

➤ Barret Rennie commented:

PR is up and awaiting review.