Add more tests for splitting ways in relations containing loops

[ockendenjo]

I've added some tests for the splitting of route relations containing loops as described in bug #4876

There are probably too many combinations of ways directions, loop traversal direction to test them all, but I can add more combinations if it's helpful.

[bhousel]

There are probably too many combinations of ways directions, loop traversal direction to test them all, but I can add more combinations if it's helpful.

Thank you @ockendenjo! Testing how iD works with more kinds of route topologies is always a great thing 👍