React|WC Parity: Combobox

[sstrubberg]

Acceptance Criteria

• Typeahead with autocomplete (new enhancement)
• Unique value (new enhancement)
• AI Label is missing gradient style
• See parent issue for more.

The above may need to be refined out into their own issues as they could be quite large

Important

Every PR needs a ux and visual review from the design team to ensure consistency. Please be sure PRs have status: visual review 🔍 applied and request a review from @carbon-design-system/design

[tay1orjones]

There are many combobox ux defects currently that we might want to address before working on parity. https://github.com/carbon-design-system/carbon/issues?q=is%3Aissue%20state%3Aopen%20combobox%20-label%3A%22type%3A%20enhancement%20%F0%9F%92%A1%22

Quite a few are listed in #18484 too