Improve the motor temperature diagnostic

[valegagge]

Is your feature request related to a problem?

As explained in robotology/icub-tech-support#2007, when a motor sensor temperature doesn't read correctly the diagnostic reports the overheating error.
In the first development of this feature, we used the same error code overheating both for the real overheating and also for error readings. The user can discriminate between the two errors checking the raw value of temperature. if is is less than zero means an reading error occurred.

In the ticker mentioned above we noticed that, only the first diagnostic error report the negative value, while the next one report the overheating error with a positive value making the user confused, if it is a fake overheating.

So, we need to avoid this misunderstanding.

The solution you would like to have available

I think the best solution is adding a different error type in the fw and then improving the diagnostic.

Alternatives you have considered

No response

Additional context

No response