feat: new package "@blueprintjs/colors"

[p-szm]

No description provided.

[adidahiya]

I fixed dist:variables by just reaching up outside of packages/core into packages/colors in the script CLI arguments. Should be ok. In a future PR we should consider adding a separate docs section for the colors package, but I'm fine with shipping this for now as we're continuing to export colors through the core package.

Note: the table test suite failures are unrelated flakes, going to investigate those more this week...