This basically changes how the xmodule static files are
generated and consumed in order to separate the Xblock
styles from general style files. Includes:
* build: decople XModule style assets by using a custom webpack loader
* build: move scss imports to its specific file
* build: fix: add system dirs to theme lookup paths. (fixes attempt 1)
* build: fix: use bootstrap variables instead of lms variables (fixes attempt 2)
This is an amendment to #32188,
which itself was an amendment to #32018.
Addressing the issue https://github.com/openedx/edx-platform/issues/31624
516eff0633