Absorb PyPI details in conda list

[jaimergp]

A lot of code in conda exists to process PyPI records for conda list. This was meant to be part of the pip_interop_enabled features that were never finished. I think we can absorb those classes here and extend them as needed without having to be hindered by the backwards compatibility policies of conda. We would deprecate all of that and instruct users to install conda-pypi if they need this functionality.

This will need several items:

• Add conda list hooks to "inject" more entries in the list before is finally printed
• Deprecate code that supports pip_interop_enabled and absorb it here
• Deprecate pip_interop_enabled key. Tell users to install conda-pypi
• See how this might affect the classic solver, if at all