Hint text in Dropdown and other input fields

### Description

When I create a dropdown there is often a need for having a hint text which shows the user what kind of options that appear if they press the dropdown list. A hint text could be "Velg politidistrikt.." and when the user presses it sees the kind of options, and if it is a required field it is not possible to leave it empty. Today you have to put this as a option in the list, but then you have to create custom validation to check if this option is selected.

### Additional Information

I want it to be similar as the date field where there is a grey text, which only works as a hint to the user, and this should be a textResourceBinding e.g "hint" for Dropdown and also be great for all kinds of input fields.

Start by locating the Dropdown and date-field implementations in the React frontend and compare how their hint text is rendered and bound to text resources. Then inspect the other input field components to determine the shared scope. Done means a hint such as “Velg politidistrikt..” is displayed without becoming an option, required dropdowns cannot remain empty, and the hint is configurable through a textResourceBinding.

Written by the indexing model from the issue text.