[4/6] build: import XModule source SCSS directly rather than copying

[kdmccormick]

Supporting information

This is a part of a series of PRs:

• Stop dynamically generating XModule SCSS #32292

The previous PR is:

• [3/6] build: stop suffixing XModule SCSS with hashes  #32288

The next PR is:

• [5/6] build: commit XModule SCSS entrypoints instead of generating them #32290

Description

The xmodule_assets command copies SCSS source files from
xmodule/css to common/static/xmodule/scss, renaming them
to {MD5_HASH}.scss in order to "remove duplicates".
The copied files are then included into the generated
SCSS entrypoint files (eg AnnotatableBlockStudio.scss).

The "de-deplication" is completely unnecessary: there are
only a couple dozen SCSS files, and none of them are duplicates.
This copying process is confusing, it complicates our
build process, and it makes our SCSS harder to understand.

So, in the generated SCSS entrypoint files, we
stop importing the copied SCSS sources, and just
import the original SCSS sources instead.
For example, common/static/xmodule/descriptors/scss/AboutBlockStudio.scss
is changed from:

.xmodule_edit.xmodule_AboutBlock {
  @import "9bdcda00f046f78be79aca7791e1d4fb.scss";
  @import "a10fc3e0fd6aca63426a89e75fe69c31.scss";
}

to:

.xmodule_edit.xmodule_AboutBlock {
  @import "editor/edit.scss";
  @import "html/edit.scss";
}

In order to make the @import lines work, we add xmodule/css to the list
of lookup dirs for XModule SCSS compilation. We also remove the
copying logic from xmodule_assets, as it is no longer needed.

Testing Instructions

• Build the Tutor openedx image with this branch
• Browse the demo course in the Studio outline editor
• Browse the demo course in Learning MFE

Deadline

Medium-high urgency, as this is in the critical path to a long line of DevX improvement PRs.

[feanil]

Change makes sense and I was able to get it up in tutor and didn't see any issues in a quick browsing of studio or the LMS.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the staging environment in preparation for a release to production.

[edx-pipeline-bot]

EdX Release Notice: This PR has been deployed to the production environment.