This change set makes the authz2 storage format the default format. It removes
most of the functionality related to the previous storage format, except for
the SA fallbacks and old gRPC methods which have been left for a follow-up
change in order to make these changes deployable without introducing
incompatibilities.
Fixes#4454.
Adds a feature which gates creation of authorizations following the style required for the new schema (and which can be used for gating the reset of our new schema code later down the road).
There was an internal discussion about an issue this creates regarding a predictable ordering of challenges within a challenge due to sequential challenge IDs which will always be static for each challenge type. It was suggested we could add some kind of obfuscation to the challenge ID when presented to the user to prevent this. This hasn't been done in this PR as it would only be focused in the WFE and would be better suited as its own changeset.
Fixes#3981.