Pass an argument by const reference instead of value and other minor fixes

[jmcarcell]

BEGINRELEASENOTES

• Minor cleanups for generated EDMs
  • Pass the argument by const reference in the relation setter
  • Remove a few includes that are not needed
  • Don't check for nullptr before deleting a (possibly nullptr) pointer
  • Remove if - else check and use implicit conversion of pointer to bool

ENDRELEASENOTES

[tmadlener]

Looks like CERNs infrastructure is slightly overwhelmed, CI is failing because we cannot get cvmfs or because fetching test data is failing.

[m-fila]

Another minor fix that could be added: this could be simiplified to just return m_obj https://github.com/AIDASoft/podio/blob/d12f4df81591e54e7750500f5d6ae70bad7ecc39/python/templates/macros/implementations.jinja2#L184-L189

[tmadlener]

Can you pick up the changes from #634 (i.e. merge / rebase onto latest master)? I think that should fix the remaining CI issues that we see.

[jmcarcell]

Can you pick up the changes from #634 (i.e. merge / rebase onto latest master)? I think that should fix the remaining CI issues that we see.

Done