Experiment the order of creation of the node type in case of out of process extension

[MarcoRossignoli]

Current architecture is creating the push node for the out of process extension before the main on in the test host.

This lead to some custom code inside VS to signal the fact that we want to discovery and not execute. In the discovery we don't want to enable out of process extension because are useless.

For now the idea is to add --list-tests to the command line to express the intent, but it should be more clean do it when we receive the request (so have a way to host the main node out of the test host node).
This is a big change in the architecture but some experimentation would be good.

cc: @drognanar