V2Tool should use Elastic-Agent server

[belimawr]

The V2Tool should use the Elastic-Agent server, this brings some advantages:

• No need to duplicate some logic from Elastic-Agent into V2Tool
• We use more of the Elastic-Agent code while testing other applications, which helps to reduce integration issues in the future.

@fearful-symmetry already made some experiments that look quite promising. More details on this comment: #41 (comment).

[fearful-symmetry]

I might need some help from @blakerouse on the shutdown, I can't get the manager object to consistently shut down a component. It's either a bug, or I just don't understand the control flow.

Other than that, it's working fine. I don't know to what degree the next sprint will de-prioritize this, but I'm currently about 80% done with it.