Fix inconsistent usage of particle mass definitions for secondary particles coming from PROPOSAL

Within proposal::InteractionModel::doInteraction(), we loop over all secondary particles produced by PROPOSAL (here) and put them on the stack (here). Note that the energy returned by PROPOSAL is a total energy. To calculate this total energy, PROPOSAL used its internal definition of the particle mass. When putting the particle on the stack, CORSIKA 8 transforms the total energy back to kinetic energies, but uses the particle mass definition of CORSIKA 8. This is inconsistent.

On the test-high-energy-showers branch (commit f4e794b4), when switching maxRadians to 0.1, using proposal/7.5.1, setting the emcut to 0.5 MeV, running radio_em_shower.cpp with 1e4 2723141261 crashed with an arithmetic exception. The reason for this was that PROPOSAL simulated a compton energy loss, where a photon transferred a very small amount of energy (~eV) to an electron (note that this is very rare). The electron mass within CORSIKA 8 is defined as 0.511MeV, within PROPOSAL as 0.5109989461MeV. Due to the inconsistent usage of the mass definitions, the electron on the stack ended up with a kinetic energy smaller than 0.511MeV (but larger than 0.5109989461MeV). This caused the crash within EnergyMomentumOperations::calculate_momentum.

With this MR, this inconsistency is solved.

added Bug EM Stack labels

This is precisely why we decided to work with kinetic energy!

Should we just go ahead and merge this then?

added 5 commits

• 9181ada6...a599430b - 4 commits from branch master
• 31196fb9 - Use proposal-internal mass definition when converting total energies to...

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resolved all threads

approved this merge request

requested review from @acoleman

added 3 commits

• 31196fb9...a198618a - 2 commits from branch master
• 4e2c74b5 - Use proposal-internal mass definition when converting total energies to...

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enabled an automatic merge when the pipeline for 4e2c74b5 succeeds

mentioned in commit 22a09a17

merged