Base it directly off of common and try to keep it as small as possible.

Regarding plugin loading:

Ideally the name of this setting would be "DEVELOPMENT" and not tied to
the devstack but since that's an interface change, we use the devstack
settings which should be what is setup for development.

Regarding the webpack loader settings:

WEBPACK_LOADER's STATS_FILE is derived from STATIC_ROOT in
openedx/envs/common.py. In the new development.py settings the base
STATIC_ROOT default is ENV_ROOT/staticfiles (LMS) and
ENV_ROOT/staticfiles/studio (CMS), which point *outside* the repo. That
is not where the webpack build writes its stats manifest: with
STATIC_ROOT_LMS / STATIC_ROOT_CMS unset, webpack.common.config.js falls
back to ./test_root/staticfiles (and .../studio for CMS). As a result
render_bundle raised "Error reading .../staticfiles/webpack-stats.json"
on every page that renders a webpack bundle.

Point STATIC_ROOT at the in-repo test_root location so the derived
STATS_FILE lands where webpack actually writes it. This makes the Python
default agree with webpack's JS default with no STATIC_ROOT_LMS /
STATIC_ROOT_CMS wiring, and mirrors what the test settings already do
(openedx/envs/test.py).

This is only about locating the stats manifest -- collectstatic is not
part of the development flow. With DEBUG=True the staticfiles finders
serve assets directly from their source dirs (e.g. the bundles in
common/static/bundles), so nothing writes into STATIC_ROOT during normal
development.