Meta-manipulation separated from compilation.

There were `Compiler >> setupClass:`
and `ClassBuilder >> setupClass:`. They did the same.
Now, `ClassBuilder` one is used exclusively.

In `install:forClass:category:`, the "set up a compiled method"
was extracted into `ClassBuilder` and was reused from other places.

Now, if you have `CompiledMethod`, you can install it without
dependency on `Compiler`.
BlockClosure >> asCompiledMethod

Allows creating CompiledMethod from a block.
Combined with previous commit's `ClassBuilder >> install:...`
it allows to add dynamic api in runtime using parametrized
block, without needing the `Compiler` to actually compile
Smalltalk source.

(in deployed scenario, there is no Compiler,
but there is a need to "compile" various kind of templates)