Fix detector name in ldmx-det-v14-8gev GMDL

[tvami]

Describe the bug

Not really a "bug" but I think it's also not fully correct. When I look at the debug printout I see

 [ Process ] 1 : RunHeader { run: 20, numTries: 32, detectorName: ldmx-det-v14, description: ECal Non-Fiducial Test Simulation

specifically I mean detectorName: ldmx-det-v14, even tho we are using ldmx-det-v14-8gev

To Reproduce

Just run the pn config from validation for example, but any config should suffice

Desired behavior

I think we just need to change this line https://github.com/LDMX-Software/ldmx-sw/blob/trunk/Detectors/data/ldmx-det-v14-8gev/detector.gdml#L109 to

<auxiliary auxtype="DetectorName" auxvalue="ldmx-det-v14-8gev"/>

Additional context

This actually would open up the possibility to get the geometry from the event header to determine geometry dependent conditions. I think would have worked out for https://github.com/LDMX-Software/ldmx-sw/pull/1245#discussion_r1581235031 (I didnt test, just an idea)