[Visual Refresh] Add Borealis theme

[mgadewoll]

Summary

Important

The changes in this PR have already been reviewed as standalone PRs.
This PR merges all changes combined to main

Included PRs

• [Theme] Base theme setup #8030
• [Visual Refresh] Setup semantic color tokens #8097
• [Visual Refresh] Update Typography scale #8103
• [Visual Refresh] Design changes #8111
• [Visual Refresh] Update vis colors and palettes #8112
• [Visual Refresh] Provide legacy JSON theme tokens #8115
• [Visual Refresh] Fix theme package builds #8120
• [Visual Refresh] Provide legacy JSON tokens via EUI #8125
• [Visual Refresh] Fix computed border token mapping #8170
• [Visual Refresh] Update color token mappings #8211
• [Visual Refresh] Introduce shared popover arrow styles to Borealis #8212
• [Visual Refresh] Add forms.maxWidth token #8221
• [Visual Refresh] Set darker shade for subdued text #8224
• [Visual Refresh] Remove support for accentSecondary badges #8227
• [Visual Refresh] Add severity vis colors #8247
• [Visual Refresh] Fix transparent color variable definitions #8249
• [Visual Refresh] Update EuiToken colors #8250
• [Visual Refresh] Add behindText vis color tokens #8253
• [Visual Refresh] Severity palette order for Amsterdam #8254
• [Visual Refresh] Fix strong border token naming #8262
• [Visual Refresh] Update floating border on EuiPanel #8270
• [Visual Refresh] Provide hooks for color palette functions #8284
• [Visual Refresh] Make Borealis default theme in EUI #8288
• [Visual Refresh] Update docs to reflect new tokens #8306
• [Visual Refresh] Fix incorrect backgroundLight json tokens #8316
• [Visual Refresh] Resolve Amsterdam specific theme imports #8318
• [Visual Refresh] Update Borealis VRT reference images #8384

Additional changes

• updates VRT reference images based on latest changes introduced in main (commit)
• fixes a missing dependency that resulted in EUI+ not being built (failing build) (commit)
• adds changelog

QA

ℹ️ Most code changes have already been reviewed separately in the respective PRs mentioned above.
Review only the additional changes.

• ci passes
• smoke test the EUI docs if anything looks broken or off
• review the changelog if the entries make sense or if anything is missing (since the changelog was composed manually from relevant changes = meaning actual impacting changes going to main)

[kibanamachine]

Preview staging links for this PR:

• Docs site: https://eui.elastic.co/pr_8386/
• Storybook: https://eui.elastic.co/pr_8386/storybook
• New docs: https://eui.elastic.co/pr_8386/new-docs

[elasticmachine]

💚 Build Succeeded

• Buildkite Build
• Commit: d90a419

History

• 💔 Build #3570 failed 3bce120

cc @mgadewoll