Fix reloading

[di]

Fixes #6578. A few things:

• Gunicorn has it's own reloader which works perfectly here, except:
• The reloader doesn't work with preload_app, which we set in our gunicorn.conf.py file, and:
• We use gunicorn.conf.py in local development, however:
• We don't need to at all, everything specified in it is overkill for local development, but unfortunately:
• Gunicorn picks up gunicorn.conf.py regardless of whether we specify it or not, so:
• We also need to rename gunicorn.conf.py to gunicorn-prod.conf.py so --reload works.

(Unfortunately we still need hupper for the celery worker due to celery --autoreload being deprecated.)

[yeraydiazdiaz]

Nice research there, thanks! 👍

[ewdurbin]

it's way faster at reloading too 👍

[di]

It seems like one downside is that until benoitc/gunicorn#2244 is fixed, any syntax error will crash the reloader, but it's still better than what we had before.