Fork FAST Combobox.

[atmgrifter00]

Pull Request

🤨 Rationale

• Refactor combobox and select for readability, code sharing, and API consistency #1948

As part of the effort to bring the Combobox implementation in alignment with the Select, namely with how we handle controlling the visibility of the options in the dropdown, as well as the need to register options as part of the connectedCallback hook, it makes sense to fork the FAST Combobox implementation into our own, as we did with the Select, to make it more clear what is happening within our own implementation for the various new behaviors we require.

👩‍💻 Implementation

Essentially bringing over the current Combobox implementation from the FAST archives/fast-element1 branch into our own. Copied the FAST FormAssociatedCombobox that our Combobox now extends.

🧪 Testing

Ran existing unit tests. Manual testing. Verified that our existing tests still replicate all of the tests currently in the FAST archives/fast-element1 repo.

✅ Checklist

• I have updated the project documentation to reflect my changes or determined no changes are needed.