TAP ambassador improvements

[LionelJouin]

Here are few tasks to improve the TAP ambassador implementation which were not part of the initial development:

• [ ] Check GRPC Connection and set unavailable status if disconnected.
• [ ] Check Conduit availability in the trench, if not existing then disconnect it.
• [x] Check the target registry to verify the streams are still open (change the status to unavailable if not and retry to open it).
• [x] Error handling. Currently the stream is removed even if there is an error, it should have a retry mechanism which stops when the context is canceled (expires...).
• [ ] First stream opened has its status set as unavailable (the time the conduit gets connected). It should be in the pending status instead (and be set to unavailable if the conduit is still not connected after a certain time).
• [ ] Monitor the NSM connection to check the IP changes

Initial issue: #135