Make Picker icon stylable and align it with visual style of modern iOS

### Feature description

Currently, the "..." icon of the picker has a prominent blue color which is not customizable. Moreover, it does not match the visual style of modern iOS anymore.


### Proposed solution

Make the color of the icon customizable to let it better integrate with various app color themes. Consider replacing it with an icon better suiting modern iOS, e.g. ">":

|Original screenshot|Annotated screenshot|
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Source: https://developer.apple.com/design/human-interface-guidelines/ios/controls/pickers#date-pickers