(REF) Extensions - Extract method to build upgrade queue

(REF) Extensions - Extract method to build upgrade queue

I was slightly concerned that building a queue under a different there are
two risks, although I don't think either is very big:

1.  That someone references the queue by name during the building process.
    However, it wouldn't make much sense from a DX POV (given how "Upgrader"
    classes are generally written), and I can't any references to
    `QUEUE_NAME` or `ext-upgrade` in `universe`

2.  That someone generates queue tasks with `weight`s that somehow clash with
    the `weight`s in core-queue. However, this also doesn't make much sense
    from a DX POV (given how "upgrader" classes are generally written).