[equals][relate] Add equals() Ls/MLs, MLs/MLs. Fix relate(L/L).

Also use relate() in equals(Ls,Ls) because collect_vectors() approach doesn't work properly for non-simple or even opposite/reversed Linestrings.

Fix how 'u' is handled in relate() in the edge case when there are more 'u' operations in the same point, also when 'u' is on the first endpoint followed by 'i' on the same IP.

Add tests for equals() and relate().