Component update: Simple list

[bekah-stephens]

• Inconsistency updates (checklist here)

• Simple List Items:

  • Update to use our action--plain--hover/selected tokens

  • Apply correct tokens (variants are currently using outdated color style here)

  • Consolidate the "light" and "dark" variants for hover/select.

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Jira Issue: PF-2476

[bekah-stephens]

Moving remaining work to the corresponding "Library theming" Jira ticket