infra: init LUCI Realms config for Angle. This doesn't yet have any effect on Angle builds/tasks, but allows to associate Angle pools with the Realms config in https://crrev.com/i/3802849 Change-Id: Id756c14e7e181cc1820cee735668949bf9567d0c Bug: chromium:1204972 No-Try: true Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2867082 Commit-Queue: Andrii Shyshkalov <tandrii@google.com> Reviewed-by: Jamie Madill <jmadill@chromium.org>