R1:3a868940c759

Add a profileimage generation workflow for the cli

Summary: Ref T10319. This adds a basic means of generating default profile images for users. You can generate them for everyone, a group of users, or force updates. This only generated images and stores them in files. It does not assign them to users.

Test Plan:
`bin/people profileimage --all` to generate all images.
`bin/people profileimage --users chad` to generate a user.
`bin/people profileimage --all --force` to force rebuilding all images.