Final planned portion of https://github.com/openedx/edx-platform/issues/34702 -- waffle flag and middleware are removed.
Commits:
1. Feature change
- Delete `content_server.use_view` waffle flag in favor of always using view
- Delete the husk of `StaticContentServerMiddleware` and references to it
- Update views module docstring
2. Refactor (move)
- Move contentserver implementation into views.py
3. Lint cleanup
- Fix import ordering (from refactor debris + amnestied lint)
b615a8767f