Add typing for load and select

[Danyal-Faheem]

Changes

• Added typing for the Entrypoint.load() and the Entrypoints.select() method.

As the Entrypoint.load() returns more than one type depending on the value of the value variable, it was necessary to set it as Any.

[jaraco]

Looks like this change introduces a couple of new errors:

________________________ importlib_metadata/__init__.py ________________________
184: error: Item "None" of "Optional[Match[str]]" has no attribute "group"  [union-attr]
185: error: Item "None" of "Optional[Match[str]]" has no attribute "group"  [union-attr]