Resolve "Fix load of geant4 libraries"

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Closes #45 (closed)


Libraries which do not exist are commented out, to get rid of warnings "library does not exist" when initiating geant4 MC

These warnings are now removed, as you can see here https://git.jinr.ru/nica/mpdroot/-/jobs/52204

ADDITIONALLY

• geant4 build tests are added (geant3 will be phased out. There is also request in FairRoot to remove geant3 tests, due to random crashes)
• strange bug which causes hang of readDST.C on c8-tests is fixed