[Visual Refresh] Support new theme tokens on JSON exports

[mgadewoll]

Summary

Important

This PR merges into a feature branch.

This PR introduces support for the new theme tokens that were added on euiTheme as well as SCSS variables already.
Initially our plan was to deprecate JSON token usage completely, which made the support for new tokens unnecessary.

But during the theme migration we noticed that there are use cases on Kibana where we can't remove the JSON token usage just yet and where the new tokens are required to support the new theme.

Note

Updating JSON tokens is currently still a manual process.

Changes

• adds relevant new tokens for: backgrounds, borders, text, data vis
• adds missing accentSecondary equivalents in Amsterdam
• reorders the tokens a bit in the JSON files

QA

I'm afraid there is no nice way to QA this besides manual checks as those tokens are not in use 🙈
But I'm confident the update is correct as the update was done as follows:

• copied euiTheme.colors output per theme and color mode and added relevant tokens to the JSON file (ensures correct color values)
• added euiColor prefixes
• rearranged tokens within the files (moving data vis colors further down right before generic color tokens)
• ensured all 4 theme files have the same amount of tokens (420)

[JasonStoltz]

Just the one comment I left.

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_8277/
• Storybook: https://eui.elastic.co/pr_8277/storybook
• New docs: https://eui.elastic.co/pr_8277/new-docs

[elasticmachine]

💔 Build Failed

• Buildkite Build
• Commit: ed061f2

Failed CI Steps

• 🔨 EUI pull request test

History

• 💚 Build #3328 succeeded 27bb394
• 💚 Build #3327 succeeded 50bf77a

cc @mgadewoll