feat(GlTokenSelector): add support for custom classes

What does this MR do?

As per: gitlab#262857 (closed) we want to implement the chevron skipping pattern for category based data in GitLab now(https://design.gitlab.com/data-visualization/color/#categorical-data).

This merges does the following:

• Revert category specific CSS and code for the tokens
• Allow GlTokenSelector to be passed a custom class set from the token data, allowing users to define classes
• Add support for the missing data-viz variables for the color palette

Does this MR meet the acceptance criteria?

Conformity

• Code review guidelines.
• GitLab UI's contributing guidlines.
• If it changes a Pajamas-compliant component's look & feel, the MR has been reviewed by a UX designer.
• [-] If it changes GitLab UI's documentation guidelines, the MR has been reviewed by a Technical Writer.
• [-] If the MR changes a component's API, integration MR(s) have been opened in the following projects to ensure that the @gtlab/ui package can be upgraded quickly after the changes are released:
  • GitLab: mr_url
  • CustomersDot: mr_url
  • Status Page: mr_url
• Added the ~"component:*" label(s) if applicable.

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• Security reports checked/validated by a reviewer from the AppSec team