The ComboBox code in components/leafy-green/combobox is currently based on the non-rebranded combobox to workaround: https://jira.mongodb.org/browse/PD-2321

To support the new brand we need to use the new component code there and remove again the buggy focus handling (https://mongodb.slack.com/archives/CFFA5BS79/p1660573498227609?thread_ts=1660573472.739789&cid=CFFA5BS79) and workaround the margin issue: See https://mongodb.slack.com/archives/CFFA5BS79/p1662450273800529 for a fix and https://jira.mongodb.org/browse/PD-2420

With the new component we also want to centralise the darkmode binding inside compass-components (as done for all the others) and get rid of the client code that applies those styles manually:
https://github.com/mongodb-js/compass/blob/bbf0c0a72a71bda2cc2b416caf51f939f4b1f7be/packages/compass-indexes/src/components/create-index-fields/create-index-fields.tsx#L177