ComboBox sends only the last element to `FieldChanged` when `MultiSelection=true`

[Mr-Technician]

As @mckaragoz and I discussed on discord, the combobox passes only the last item into FieldChanged, as this method is called within SetValuesAsync of the MudBaseInput (see). I would consider this a bug and inconsistent with the core library, where the entire selection is passed to FieldChanged: https://try.mudblazor.com/snippet/cumzEgmpzlCHQSWe

An example of where this occurs within ComboBox is: https://github.com/CodeBeamOrg/CodeBeam.MudBlazor.Extensions/blob/dev/CodeBeam.MudBlazor.Extensions/Components/ComboBox/MudComboBox.razor.cs#L1237

I'm open to discussion on this issue.