Refactor package names

[angelhof]

Do a refactoring pass where we change package names (we need to do this in file names and setup.py). Currently, most packages contain _new in the name (which should be removed) and also they should be moved under pash_annotations (or annotations) in the directory, so that users can import them as import pash_annotations.parser instead of import parser_new (which could be a package from an arbitrary library that has nothing to do with PaSh).

Also, we should rename main.py to something like annotation_cli and also include it in the pip package (by adding it to setup.py).

@festutz could you take a stab at those changes in a PR that is targeted to main?