tidy xAODEgamma,xAODTracking,xAODCaloEvent

The only "non 100% trivial" change to understand is adding

     virtual ~IParticle() = default;
     // since we have a dtor default or delete
     // the others
     // AuxElement has copy ctor and
     // assignement but not move
     IParticle() = default;
     IParticle(const IParticle&) = default;
     IParticle& operator=(const IParticle&) = default;
     IParticle(IParticle&&) = delete;
     IParticle& operator=(IParticle&&) = delete;

instead of

virtual ~IParticle() {};

Actually , since the base does not have move operations and we had a dtor, the moves were already "suppressed". ( can not see any "move" for xAOD objects which prb makes sense.)

The other were there (defaulted). So this makes a bit more explicit what is there

The reason is that since copy ctors of derived classes were using the base defaut ctor (assuming there was not default copy ctor for the base I guess .. ) , there were warnings since for clang-tidy this falls under "bugprone" . i.e clang-tidy complains when one uses the "wrong" base ctor ,default rather than copy, when declaring the copy ctor for the derived class. I can imagine why this is considered "bug prone" ...

In short I followed this https://github.com/isocpp/CppCoreGuidelines/blob/master/CppCoreGuidelines.md#Rc-five and yes is a few more lines but bit more clear what is "there".

Then there are:

• some 0-> nullptr
• uses of size() --> empty()
• white space removals (you can hide them for the review via the tick box on )