If a user is a admin or owner, show them in assignee task dropdown

Right now, when team members are admins or owners, when you try to add them, assign them to a task, they don't show up in the task unless you go to the project settings, type their email address in, and add them to the project. We need to refine this flow. We got a couple of options:

1. We could make it to where we just show all owners and admins in the assignee dropdown, even if they're not on the project.

2. We make it a lot easier to add people who are on the team to a project.

Those are our two options. We gotta think through it and make it right.