line name to number map should be sorted

Changing the order of lines results in an new encoding key which is not strictly needed.

/cc @oozcelik

added RTA WP5 rta-operations labels

I think @raaij implemented a sorting in !1428 (merged), but there were too many tests needing a ref update, so we decided to decouple in order to get the MR faster. Now might be a good time to implement it in a dedicated MR.

mentioned in merge request !1480 (merged)