Mark "v3" API methods as stable; mark obsoleted methods as "Frozen"

Summary:
Ref T12074. The "v3" API methods (*.search, *.edit) are currently marked as "unstable", but they're pretty stable and essentially all new code should be using them.

Although these methods are seeing some changes, almost all changes are additive (support for new constraints or attachemnts) and do not break backward compatibility. We have no major, compatibility-breaking changes planned.

I don't want to mark the older methods "deprecated" yet since arc still uses a lot of them and there are some capabilities not yet available on the v3 methods, but introduce a new "frozen" status with pointers to the new methods.

Overall, this should gently push users toward the newer methods.

Test Plan: {F2325323}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12074

Differential Revision: https://secure.phabricator.com/D17158