meshkernel contacts in Network instance created from netfile

[veenstrajelmer]

Is your feature request related to a problem? Please describe.
Currently, the contacts of the Network._link1d2d.link1d2d and the Network.link1d2d.meshkernel.contacts_get() are out of sync when reading a network file. The latter is empty, because the meshkernel contacts are not set upon reading the network. This is not implemented in meshkernel yet: Deltares/MeshKernelPy#107

Describe the solution you'd like
After implementation of contacts_set() in meshkernel we can use it in UgridReader.read_link1d2d(). If implemented there, the two contacts administrations should be in sync again and the assertions in test_create_1d_2d_1d2d can be uncommented. Also, the two plots should be the same (currently the second one misses the contacts).