Refactor css variables for all components to reflect ADR.

Description

Refactors all usage of CSS Variables to comply with https://github.com/phase2/phase2-adr/pull/17

Components affected:

outline-admin-links
outline-alert
outline-breadcrumbs
outline-button
outline-dropdown
outline-link
outline-list

In addition to supporting the naming convention listed in the ADR, especially around the use of --computed, also modified the styles.js script to avoid adding :host{} around files in the css-variables folder in favor of putting the :host directly in the vars.css files themselves. This change:

allows the vars.css files to be directly imported into the component main css file, avoiding the need for using componentVars in the typescript file
supports future functionality of styling in the light DOM.
removes "magic" from the build process.

Type of change

Please delete options that are not relevant.

[ ] Bug fix (non-breaking change which fixes an issue)
[ ] New feature (non-breaking change which adds functionality)
[X] Breaking change (fix or feature that would cause existing functionality to not work as expected)
[X] This change requires a documentation update

This is a breaking change for any project currently using the new mono repo and overriding CSS variables since some variables have changed names.

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Provide instructions so we can reproduce. Please also list any relevant details for your test configuration

[X] Visual Testing
[ ] Automated Testing
[ ] Accessibility Testing

Checklist

[X] My code follows the style guidelines of this project
[X] I have performed a self-review of my own code
[X] I have commented my code, particularly in hard-to-understand areas
[X] I have made corresponding changes to the documentation
[X] My changes generate no new warnings
[ ] I have added tests that prove my fix is effective or that my feature works
[ ] New and existing unit tests pass locally with my changes
[ ] Any dependent changes have been merged and published in downstream modules

phase2 / outline