LogBrowser: show errors and events for Rover-4.0

In Copter, Rover, Plane-4.0, all vehicles can log the same Events and Errors as Copter does.

The consolidated list of Error Subsystems is here: https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Logger/AP_Logger.h#L104
Error codes are here but I think MP simply displays the number which is fine: https://github.com/ArduPilot/ardupilot/blob/master/libraries/AP_Logger/AP_Logger.h#L138

Below is an image from a Rover log that suffered from an EKF variance (ErrorCode 16) and then the EKF failsafe was triggered (ErrorCode 17) but these aren't visible in the log when filtering by Err. Also the little red marks don't appear at the top


Start in the Mission Planner LogBrowser and compare its handling of Rover-4.0 logs with the subsystem and error-code definitions in libraries/AP_Logger/AP_Logger.h, linked in the issue. The work is done when Rover events and errors appear when filtering by Err and the corresponding red marks appear at the top, as shown for Copter.

Written by the indexing model from the issue text.