Allow users to search in config flow selector

[tjorim]

Some integrations will ask a user to select something from a list.
This list can sometimes be very long requiring a lot of scrolling.
Example:

Unlike other selectors in the UI (area/labels/category) there is no way to search.
Example:

Ideally the config flow also allows a user to search in a selector field.
This was also briefly discussed in the Discord beta channel.