Simplify part of, type and cleanup py2d.py

[Avasam]

Split off from #2384 (which only aims at updating online docs with 307).
Helps towards #2432

This PR:

• Adds type annotations to py2d.py for development and IntelliSense convenience
• Does the DocInfo initialization work in the DocInfo.__init__ method
• Creates a subclass of DocInfo to do the same for argument infos generated by the BuildArgInfos method
• • Simplifies usages of should_build_function
• Simplify print calls as sys.stdout is already the default when file=None

Edit: I can simplify this into smaller chunks for ease of review.