fix signal handling in wait() on calls to stop()

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #11286
| License       | MIT
| Doc PR        | 

``wait()`` throws an exception when the process was terminated by a signal. This should not happen when the termination was requested by calling the ``stop()`` method (for example, inside a callback which is passed to ``wait()``).
The purpose of the bug fix is to avoid sending an exception when the underlying process is signaled by the process component.
When we call the `Process::stop` method, we just send a signal to the underlying process.

`kill` is excatly the same as our `Process::signal` method : it sends a signal to a process.

Using the way I propose, any signal sent outside the Process component (using kill for example) would trigger the exception, not the ones sent by the Process component

Hope I'm clear enough :)