Enhancement: Add support for flush action lists

[gwwar]

Enhancement: Add support for flush action lists

[github-actions]

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[langermank]

Thanks for opening this issue! We discussed this during our weekly React sync, and feel that we are unlikely to support a flush ActionList unless we have more cases to support. All new Primer menu components include internal padding, so ActionList styles are never full width and maintain the built in border-radius on each item. This menu could probably use a similar treatment. Closing for now and we will reopen if we decide to pursue in the future!