Use log level error to report telemetry

[cecton]

Please beware that if you do -loff,telemetry=trace it still fails!

./target/debug/substrate --dev --tmp --telemetry-url "ws://127.0.0.1:1337 10" -loff,telemetry=trace
2021-02-10 12:55:03.801  ERROR main telemetry: Could not initialize telemetry: the span could not be entered    
2021-02-10 12:55:03.807  ERROR tokio-runtime-worker telemetry: Received connection notifier for unknown node (/ip4/127.0.0.1/tcp/1337/ws). This is a bug.    

It just doesn't fail anymore for -lerror and -lwarn

Fixes: #8093

[bkchr]

As already discussed in element. @cecton will work after this on some pr to move telemetry out of this tracing infrastructure. Instead of doing this, we will pass a telemetry object around as we do for prometheus.

[gnunicorn]

bot merge

[ghost]

Trying merge.