Use sass-embedded to solve the optimizer performance issue with dart-sass

[abbyhu2000]

Is your feature request related to a problem? Please describe.

This is a follow up issue to #2223

After changing from node-sass to dart-sass, the first time compilation time has increased exponentially (from around 50s to 400s). One possible solution is to add a node-fiber package to improve the performance (#2319). However, node fiber will only be supported with node 14. For node 16 and later versions, we can explore the option of using sass-embedded package.

Describe the solution you'd like

Better performance and shorter time for the first compilation

Additional context
https://www.npmjs.com/package/sass-embedded

[abbyhu2000]

@AMoo-Miki I tried using embedded-sass, and the first compilation still took around 300s, which is not a lot of improvement from the original.

[ashwin-pc]

Hmm, this makes me wonder if the issue is not with how fast the sass compiler is, but rather how osd-optimizer compiles them. What fibers did was allow sync operations to happen asynchronously. Which must mean that we must have an inefficient optimizer loop thats bottlenecking us.

[AMoo-Miki]

For now, we have used a custom patched release of sass-loader and node-sass but this issue has to be revisited since node-sass is deprecated already.