How to get custom post type categories in an array

You can use get_terms() to retrieve the custom taxonomy terms and then build up a custom array to match the structure you want.

Try this:

//Get the custom taxonomy terms
$taxonomies = array(
    'name' => 'your_custom_taxonomy' //Edit to match your needs
);

$taxonomy_terms = get_terms( $taxonomies );

//This array will store the results
$taxonomy_array = array();

//Parse the terms
foreach ( $taxonomy_terms as $taxonomy_term ) :

    //Get the taxonomy term name
    $taxonomy_term_name = $taxonomy_term->name;

    //Get the taxonomy term slug
    $taxonomy_term_slug = $taxonomy_term->slug;

    //Push the custom array
    $taxonomy_array[ $taxonomy_term_name ] = $taxonomy_term_slug;

endforeach;

The data will be stored in $taxonomy_array following the format you provided. You can pass additional arguments to get_terms(), such as the order.