AssignmentTexter refactor

[schuyler1d]

Part of https://github.com/MoveOnOrg/Spoke/issues/1533

Description

This moves a BUNCH of files around -- every component that is only used for the texter's contact screen is moved into components/AssignmentTexter/

I think the main question in this PR is how do we want to organize components/containers further?
I think @lperson started doing work that grouped these things. While this still groups things in containers/components division is it better to group even further and lose the distinction between container and component (which I don't think we're perfect on) or group them all together (in this case it would move the directory into containers/ and then everything would be under, e.g. TexterTodo/

Do folks have bikeshed thoughts on organization here?

Checklist:

• I have manually tested my changes on desktop and mobile
• The test suite passes locally with my changes
• [na] If my change is a UI change, I have attached a screenshot to the description section of this pull request
• My change is 300 lines of code or less, or has a documented reason in the description why it’s longer
• [na] I have made any necessary changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• My PR is labeled [WIP] if it is in progress

[matteosb]

Looks great, I'm all for this grouping. IMO the containers/ components distinction isn't particularly useful right now. I'd prefer to see components used only for those components that are designed to be re-usable and ideally stateless, while keeping all "private" components grouped with containers.