Have the WFE ask the RA for authorizations, rather than asking the SA
directly. This extra layer of indirection allows us to filter out
challenges which have been disabled, so that clients don't think they
can attempt challenges that we have disabled.
Also shuffle the order of challenges within the authz objects rendered
by the API. We used to have code which does this at authz creation time,
but of course that was completely ineffectual once we stored the
challenges as just a bitmap in the database.
Update the WFE unit tests to mock RA.GetAuthorization instead of
SA.GetAuthorization2. This includes making the mock more accurate, so
that (e.g.) valid authorizations contain valid challenges, and the
challenges have their correct types (e.g. "http-01" instead of just
"http"). Also update the OTel tracing test to account for the new RPC.
Part of https://github.com/letsencrypt/boulder/issues/5913
cac431c661