Finish working out the RSA-PSS example in terms of what it implies about the
interface. The key takeaway is that a mixed-domain module must support
algorithms if they are available through either interface, and that's all
there is to it. The details of how dispatch is done don't matter, what
matters is only the availability, and it's just the disjunction of
availabilities.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>