Label and supporting_text properties on date picker

[steininge]

Is your feature request related to a problem? Please describe.
it would be great if date picker had label and supporting text, like text boxes. That would make input forms consistent, more compact and better looking.

This form would look better with label and supporting text on the date pickers:

[bcm628]

Right now, the DatePicker is a just the Anvil DatePicker with restyling, so we can't easily add those properties. We should prioritize implementing an M3 DatePicker, though.