add spack post-installation testing

This Merge Request:

• adds or fixes tests for most EBRAINS (top-level) Spack packages
• adapts gitlab CI and installation script to run tests at installation time

packages/py-elephant/package.py

 # Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
-# Spack Project Developers. See the top-level COPYRIGHT file for details.
+# Spack Project Developers. See the top-level COPYRIGHT file fr details.
 #
 # SPDX-License-Identifier: (Apache-2.0 OR MIT)