fix event listeners in net plugin

[rochdev]

This PR fixes the following issues with event listeners in the net plugin:

• The event listeners would not be cleaned up after the span is finished. When sockets are reused, this would lead to new event listeners constantly added and never removed.
• The close and timeout events were not handled. This could cause a memory leak if the socket was destroyed or timed out since the span would never be finished.

Since the lookup event cannot be reliably associated with the correct span when connect() is called multiple times, the tcp.remote.address tag was moved to the dns plugin instead as a new dns.address tag.