Use @primer/primitives v8 colors with fallbacks

[langermank]

What are you trying to accomplish?

Utilizes updated stylelint plugins to upgrade to the new primitive v8 tokens. Fallbacks for the legacy colors are added at build time.

What approach did you choose and why?

yarn run stylelint:fix and some find/replace

What should reviewers focus on?

Fallback values are added via PostCSS at build time. Should we be concerned about the impact this could have on people using our SCSS files directly?

Can these changes ship as is?

• Yes, this PR does not depend on additional changes. 🚢

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1167d5d

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[langermank]

Closing in favor of #2466