Together, these changes make it so that all features of the Paver-based
asset compilation system are supported with drop-in Paver-free
replacements. The remaining Paver asset functions are trivial wrappers,
which can be comfortably deleted before Sumac.
* Turn `./manage.py ... compile_sass` into a simple wrapper around `npm
run compile-sass`
* Turn `paver webpack` into a simple wrapper around `npm run webpack`
* Turn `pavelib.assets:collect_assets` into a simple wrapper around
`./manage.py ... collectstatic`
* Add/improve deprecation warnings for all Paver asset commands.
* Load defaults for asset-related Django settings from environment
variables. This allows the build to work without Python. For the
settings which will be removed in Sumac, I've added deprecation
warnings.
* Change EDX_PLATFORM_THEME_DIRS env var to COMPREHENSIVE_THEME_DIRS.
This simplifies the migration instructions, because all the new env
vars now match their corresponding Django settings. This amends an
ADR, but it should not be a breaking change because the env var was
recently added (since Quince) and nobody should be using it yet.
* Future-proof the static assets ADR with links. The linked pages will
be kept up-to-date even if the ADR isn't.
Part of: https://github.com/openedx/edx-platform/issues/34467