add ATLAS_CHECK_THREAD_SAFETY to TRT_ElectronPidTools

This MR is about adding ATLAS_CHECK_THREAD_SAFETY to the TRT_ElectronPidTools

The real issue was the line

HTcalculator* HTcalc = const_cast<HTcalculator*>(*readHandle);

the const_cast was there so as to allow this check

HTcalc->checkInitialization()

• Here I Assume that the check is really needed i.e it can have an effect at certain cases. Then one has to make the checkInitialization also const. One way to do it is via "double checked locking", check if valid, lock, recheck do work and set valid.

• If the check is not really needed or at some stage turns is not needed, then things can be simplified i.e the HTcalculator checkInitialization can remain non-const

For good measure I also added ATLAS_CHECK_FILE_THREAD_SAFETY to the HTCalculator

Mentioning @oda as I know he has been looking at codes like this.