Split out `djangorestframework` tox group

[alexander-alderman-webb]

The maintainer doesn't seem very active, and we should remove the upper bound on Django here:

sentry-python/scripts/populate_tox/config.py

Line 125 in 52a7c26

"include": "<6.1b1",

[linear-code]

PY-2666

[MrMithun101]

Hi! I'd like to work on this if it's still open.

My understanding: djangorestframework is currently just a version-pinned dependency string inside the django entry in scripts/populate_tox/config.py, so its test coverage is tied to whichever Django version window is active rather than being exercised against its own supported range. My plan would be to:

1. Add a standalone djangorestframework entry to TEST_SUITE_CONFIG, with its own deps/version constraints
2. Register it in GROUPS in scripts/split_tox_gh_actions/split_tox_gh_actions.py
3. Add a _MIN_VERSIONS entry in integrations/__init__.py if one doesn't already exist for DRF
4. Regenerate tox.ini via scripts/generate-test-files.sh and commit the result

One question before I start: should removing the <6.1b1 upper bound you mentioned be part of this same PR, or is that a separate follow-up once DRF has its own group? Want to make sure I keep the PR scoped to one thing.

Happy to adjust the approach if I'm missing context on how this should be structured, let me know if this sounds right and I'll get started.