Dart sass

[jgoz]

Description

Switch to Dart Sass so that the web console can be compiled on Mac arm64 architectures.

This necessitated two changes:

• Shim the svg-icons function because we don't have access to it. Apparently it's possible to use from Blueprint's build system but this also requires copying the icon SVG files into the repo since they're not included in npm. It was simpler to render transparent for these, since the function was only being used for breadcrumbs and the Web Console doesn't use Blueprint's breadcrumbs (AFAIK)
• Upgrade Blueprint to pull in these changes that make its scss source compatible with Dart Sass

I also ran sass-migrator to clean up deprecated syntax in our local scss files.

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This PR has:

• been self-reviewed.
• been tested in a test Druid cluster.

[vogievetsky]

This is awesome. Thank you so much for doing this. Everyone out there developing Druid on an M1 Mac salutes you.

(sent from my Intel based mac)