Switch to new style type hints

[sentrivana]

Problem Statement

Once we've removed support for EOL Python versions, we can migrate our type hints from comments to new-style typing hints.

Solution Brainstorm

• research tools to do this automatically
• if there is no tool or it doesn't work great for us, start a gradual rewrite and come up with a plan (e.g. everyone who touches a function needs to update its typing hints, etc.)

Note

This is optional but nice to have for 3.x, depending on how much work it is.

[sl0thentr0py]

taking this for a spin with cursor