A.K.A "translation keys instead of content keep showing up and flashing to the localised version on first load"

Use new/extended js-modules/js-builder API delivered as part of JENKINS-39322 to automatically coordinate the async loading of i18n translations as part of the loading of a blueocean bundle that depends on the translation.

This will allow synchronous access to the translations at runtime (because we can guarantee that they are already loaded in the browser), which in turn allows a much nicer programming model around i18n, removing the need to tie translation resource loading into react lifecycle etc (i.e. no need for e.g. react-i18next shim for react components - would need something else for non react components).

Assigned to tfennelly for now, but should be doable by anyone if we get JENKINS-39322 right.