Persist in the event header if we are running on real data & make a CI test for it

[tvami]

Is your feature request related to a problem? Please describe.

We need to separate real data from simulated data, and also add a CI that tests for it

Describe the solution you'd like

Implement a new function in the EventHeader that keeps track if we are running on real data + add CI as test

Additional context

Came up here https://github.com/LDMX-Software/ldmx-sw/pull/1426/files#r1741047536

Run on data

ldmx recompFire TrigScint/exampleConfigs/runQIEDecode.py /fs/ddn/sdf/group/ldmx/data/TS-data/test_stand_data/rootFiles/unpacked_ldmx_captan_out_09-04-2022_09-36-04__75_reformat_30timeSamplesFrom0_linearize_hits_clusters.root out.root raw 1 TrigScint/data/channelMap_LYSOback_plasticFront_12-to-16channels_rotated180.txt