charm: allow for juju-info relation

We add a bundle that uses it for verification (and because we wanted
another simple bundle anyway).

As a drive-by fix, we change VerifyWithCharms to make it easier
to verify without verifying constraints.

Oh I see what you were getting at. I don't think it really needs a comment though - I don't think there's any implication anywhere that ep0 and ep1 are ordered.