Fix CSS & JS deprecation warnings following node upgrade

[gabrielcld2]

Due to the recent node upgrade, several deprecation warnings were being shown.
These are now addressed here.

Approach

• Replace render with createRoot
• Migrate SCSS @import to either @use or @forward
• Replace SCSS deprecated color functions

Note: there are two warnings left due to file sizes. These might have to remain for now:

1. The cloudinary CSS file was already quite large. Splitting it into smaller files might be a bit more complicated.
2. syntax-highlight.js is large due to the CodeMirror dependency. That file is thankfully only enqueued on the admin page requiring it only, so perhaps we can leave with this for now.

QA notes

• Run npm run build to make sure assets are still building and not showing warnings (except for the two file sizes mentioned above)
• Do some regression testing on Cloudinary settings pages, the editor, and the frontend.

[PatelUtkarsh]

LGTM!

Build is clean, all Sass warnings are gone. Tested locally and everything looks good.