Sass embedded 1.78.0 should allow to replace the pure js implementation

[sveetch]

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

Recent dart-sass-embedded version finally include an executable that would allow to use it instead of the pure js implementation. The embedded host will be largely faster that the pure js one.

https://github.com/sass/dart-sass/blob/main/CHANGELOG.md#embedded-sass-2

Describe the solution you'd like

Use the embedded host instead of the pure js so it will fasten the CSS builds.

Additional context

However, embedded host or not won't fasten the build inside webpack that is more slower because of the JS pipeline.

[sveetch]

Worth to notice that with >1.77.6 there is a lot of new deprecation warning that we will have to silence. Bootstrap does not seems inclined to fix (see issue bootstrap/issues/40962) this before a new major release that we will wait for a long time. But the sass embedded performance feature seems more important.