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.
This is an amendment to #32018
Addressing the issue #31624
c34f8efc0e