RAW_NS: rework NS connection to use NS_Provider

Previous RAW_NS only supported NS over UDP because
it handled the UDP connection on it's own.
Because of this there was no cleanup function for the tests
because no virtual component were started.
Using the new NS_Provider allows to use the same tests over
UDP and FR with no changes.

Change-Id: I8a3b6c72798a75f434f54229fdbfc802cd13967e
12 files changed