Add short-circuit hook in GP_Original::closest_original

[gedex]

This would allow us to swap string similarity algorithm. The hook can be placed early in the closes_original()

https://github.com/GlotPress/GlotPress-WP/blob/6d86cc2c37515a482633220b1501bd588fefd43c/gp-includes/things/original.php#L397-L401

with something like:

$pre = apply_filters( 'pre_gp_original_closest_original', false, $input, $other_strings ); 
if ( false !== $pre ) {
    return $pre;
}