Integration Tests only: nxos_udld, nxos_udld_interface, nxos_vxlan_vtep_vni (#29143)
* it cases for vxlan_vtep_vni, udld
* platform specific testing
* fix vxlan_vtep for n7k
* fix udld_intf setup
* skip udld tests on titanium n7k
* remove hardcoding
* fix udld tests for titanium
