Support for unmanaged nodes

[chkeita]

This feature will let external nodes connect to a Onefuzz instance.
The goal is to allow users to use their own compute resource take part in the fuzzing process.
This will unlock the possibility of using vm_sku and os not available in azure. It can also help some advanced debugging scenarios in the agent

implementation discussed here #2483

• Unmanaged node receive multiple stop message after it shuts down #2995
• Allow the logs of the task to be redirected to the console #2996
• Add the ability to validate/run a task locally #2944

continuation of #2482

AB#46481