Upgrade django-debug-toolbar

- Upgrade edx-drf-extensions to 2.4.5
- Removed constraint to 2.4.0, because 2.4.2 introduces a workaround for
ARCH-1210 by putting the problematic code behind a django setting.
- Remove unused JWT_AUTH_REFRESH_COOKIE setting.

ARCH-418, ARCH-1269, ARCH-1044

fix broken toggle

guincorn just released its version on 9th-nov-2019 (20.0.0)
and it requires Python 3.x >= 3.4.
so adding constraint < 20.0.0

execute make upgrade

We also pin back edx-lint to fix a regression we introduced when we
started having to roll back all the requirements changes.

Issue 851 seems to have been resolved and issue 8.5.2 while still open is
not occuring with the latest version of pip-tools.

PROD-533

Getting 500 error on stage after upgrading to latest version
of newrelice.

We had to pin json diff because of how we pull prod requirements into
testing.txt

Both python 3 related but different reasons. numpy dropped python 3
support and faulthandler was pulled into python in python 3.3

* Updating Python Requirements

* Don't rely on pip-compile cache

* Fix tornado dependency resolution

Bumping edx-organizations will add history to the Organization model.

DE-1510

This also pins scipy to version <=1.2.1 in constraints.txt, as 1.3.0 requires py3.5 or above

was causing issues with PT exam configuration dashboard launch

Extra constraints needed to be added for pytest-randomly and tornado,
both of which have dropped Python 2 support.