feat(Tracing): use NoopTracer by default

[camilledejoye]

Currently if we don't provide a tracer provider to the Tracing class when we try to trace something we got an exception. This forces us to configure the Tracing class in our unit tests to avoid this exception.

This PR propose to use the NoopTracer provided by open telemetry instead. In addition I also propose to always use the same tracer instance instead of creating a new one every time, it's already what open telemetry does as we can see with the NoopTracer::getInstance().

[cdaguerre]

@camilledejoye do you want to rebase this?