(PUP-3433) Don't store autoload instances

Autoloader instances were being stored in the Autoload class instance,
but no code actually used the stored values. We can remove all of that
logic.
(PUP-3433) Remove method proxying methods

Why write a 3 line method when you can write a 12 line metaprogramming
method?
(PUP-3433) Remove invocations of Autoload with explicit wrap

In Kernel.load, the wrap argument defaults to false and it was never
possible to set it to true.
(PUP-3433) Tear out dead wrap code

In the class instance `@wrap` could never be true, and in instances
`@wrap` was never used.