Deprecating amber_vm

This makes `amber_vm/{smalltalk,nil,_st,globals}` deprecated. It also uses `amber/boot` instead of `amber_vm/boot`. It only lists `amber/boot` as a dependency and takes all these values (globals, vm, _st function) from it.

Includes backward compatibility, where it still can load libraries compiled with use of `amber_vm` internal namespace.

(compiler not yet updated, but all is ready for changing the prologue)