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)