refactor(millercolumns)!: tokens migration

[jenndiaz]

Description

Migrates the MillerColumn component

Also:

• updates asset list storybook to correctly display Files Selectable variant

Jira Ticket 509

Does not address issues within the asset list, added comment to Jira ticket for the Asset List migration detailing issues.

How and where has this been tested?

Please tag yourself on the tests you've marked complete to confirm the tests have been run by someone other than the author.
Tested by @jawinn

Test Outline

1. Open the docs site for the MillerColumns component:

• component should match the production docs site

1. Open the storybook site for the MillerColumns component:

• No changes to branches Selectable
• Files Selectable should show checkmarks on the right and only for files (no check marks on folders/asset item with the right chevron)

Regression testing

Validate:

1. A legacy documentation page (such as accordion), including:

• The page renders correctly
• The page is accessible
• The page is responsive

2. A migrated documentation page (such as action group), including:

• The page renders correctly
• The page is accessible
• The page is responsive

Screenshots

To-do list

• I have read the contribution guidelines.

• I have updated relevant storybook stories and templates.

• I have tested these changes in Windows High Contrast mode.

• If my change impacts other components, I have tested to make sure they don't break.

• If my change impacts documentation, I have updated the documentation accordingly.

• ✨ This pull request is ready to merge. ✨

[github-actions]

🚀 Deployed on https://pr-2191--spectrum-css.netlify.app

[jawinn]

Looks good to me! The only two things I saw were what you already found that are related to AssetList and not this component (dark themes appearance and indicating keyboard focus).

[jawinn]

These two could be renamed with logical property naming? e.g. --spectrum-millercolumn-margin-inline-start