Limit combobox and select dropdown to 10.5 visible options

[m-akinc]

Pull Request

🤨 Rationale

Fixes #1870

👩‍💻 Implementation

In setPositioning, where maxHeight of the listbox was already being calculated, now limit to maximum of 10.5 visible items. For a filterable select, the height of the filter adds to the height of the listbox, i.e. we still show 10.5 options. If a select contains grouped options, extra space is not reserved for group headers, meaning fewer than 10.5 options may be visible. This results in a simpler implementation and prevents height changes/jiggle when typing in the filter box and more than 10 options are matched.

🧪 Testing

Added visual tests for the height limiting behavior, including with/without filter input and above/below.

✅ Checklist

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

[m-akinc]

@atmgrifter00 mind buddying this?

[m-akinc]

@NIbokeefe sorry, I reset your vote without thinking. No action needed on your part.