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

podio/python/templates/macros/implementations.jinja2

Lines 184 to 189 in d12f4df

	bool {{ full_type }}::isAvailable() const {
	if (m_obj) {
	return true;
	}
	return false;
	}

[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