Support Date/DateRange BaseFieldDefinitions

Problem/Motivation

When the FullCalendar view looks at fields to determine if they are of type date or daterange, it checks whether they are an instanceof FieldStorageConfig, which is not true for BaseFieldDefinitions.

if ($field_definition instanceof FieldStorageConfig) {
    return in_array($field_definition->getType(), ['datetime', 'daterange']);
}

Proposed resolution

We should instead check for instanceof FieldStorageDefinitionInterface which includes BaseFieldDefinitions.