Make combobox and select dropdowns float above other UI

[m-akinc]

Pull Request

🤨 Rationale

Fixes: #606
Fixes: #1227

👩‍💻 Implementation

I initially looked at using Floating-UI, as that is what FAST 2.0 is using to solve this problem. (see #1234) However, for consistency, that would require adding support to both the Select/Combobox as well as updating the menu button, the menu item (for submenu support), and the tooltip. Each case was a significant change, and I ran into several problems, including with the action menu in the table. It turned into a 40+ file change with a lot of risk. I sunk more time into it than I wanted, and still didn't feel close to done. I'm instead taking a much more scoped approach of extending the existing pattern and using the anchored region in the Select and Combobox.

This required forking the templates for both controls from FAST, so that we could add the anchored region element.

🧪 Testing

I added some tests to cover certain expectations about the templates, e.g. attribute forwarding. I'm relying mostly on existing Chromatic tests to ensure the listbox pops up in the same place given the position options.

✅ Checklist

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