Relocate "passlib.handlers" into "passlib.hash"
It's kinda unexpected to users that "passlib.hash" is the public location where hashers are imported from; but when people dive into the source, the actual class definitions are over in "passlib.handlers".
Would like to make "passlib.hash" into a package, which contains all the definitions (perhaps as private modules, e.g. "passlib.hash._bcrypt", and so on). But would still like to preserve the "lazy loading" behavior that "passlib.hash" currently exhibits.
At the same time, might be a good opportunity to move some of the hardcoded bits of the lazy loading instrumentation out of "passlib.registry" and into "passlib.hash" proper; so it can be right next to the IDE inspection hints.
Leaning towards doing this, but enough machinery will need to be altered that it will be delicate, if doable at all. Additionally, it'll be very disruptive for merging any pending changes from other branches. So this should probaby be deferred until very close to v1.8's release date, to minimize any merge work that has to be done.