Feature request: add protection level message parsing

[gennartan]

Describe the solution you'd like
Forward the protection level data on a specific topic. The output of the protection level is published through the UBX-NAV-PL message. This would be a good way to ensure localization reliability when safety is required. The ublox feature is described in [1].

Describe alternatives you've considered
Localization precision is also given by h_acc and v_acc. But it is not sufficient for safety in some applications. We also noticed that those values could be too small compared to real position estimate.

Additional context
As described in [1], the protection level feature is designed for robotic applications that requires reliability in the precision of the localization. This feature would therefore be required soon. With this ticket, I hope to accelerate the integration of this feature to be able to use it with my robotic application soon.

[1] https://www.u-blox.com/en/technologies/protection-level