Add client chain element to monitor dead NSEs

[NikitaSkrynnik]

Description

Added a new client chain element that monitors NSE it has a connection to. If it get deleted:true event from the registry for this NSE it calls Close to close the client side of the connection to the NSE.

Original goal is to close leaked connections from vl3 NSEs to dead vl3 NSEs in the vl3 Network (because vl3 network doesn't have healing.

Issue link

networkservicemesh/cmd-nse-vl3-vpp#289

How Has This Been Tested?

• Added unit testing to cover
• Tested manually
• Tested by integration testing
• Have not tested

Types of changes

• Bug fix
• New functionality
• Documentation
• Refactoring
• CI

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

❗ No coverage uploaded for pull request base (main@90f0c79). Click here to learn what that means.

❗ Current head 2be5d6c differs from pull request most recent head bb2a5e3. Consider uploading reports for the commit bb2a5e3 to get more accurate results

Additional details and impacted files

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  Coverage        ?   67.25%           
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  Files           ?      261           
  Lines           ?    12382           
  Branches        ?        0           
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  Hits            ?     8327           
  Misses          ?     3530           
  Partials        ?      525           

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