Short description of the MR

Update dependencies

Update the version of deps according to our policy: oldest supported Ubuntu & Fedora, oldstable debian & spack 0.18
switch to a new test environment docker image with these deps
Do not support embedded doxygen anymore
Directly use vendored gtest, benchmark & ZPP with add_subdirectory

List of things to check before making a MR

Before merging your code, please check the following:

[x] you have added a line describing your changes to the Changelog;
[x] you have added unit tests for any new or improved feature;
[x] you have checked pdi/docs/CheckList.md
you have checked your code format:
- [x] you have checked that you respect all conventions specified in CONTRIBUTING.md;
- [x] you have checked that the indentation and formating conforms to the docs/formating.astyle;
- [x] you have documented with doxygen any new or changed function / class;
you have correctly updated the copyright headers:
- [x] your institution is in the copyright header of every file you (substantially) modified;
- [x] you have checked that the end-year of the copyright there is the current one;
you have updated the AUTHORS file:
- [x] you have added yourself to the AUTHORS file;
- [x] if this is a new contribution, you have added it to the AUTHORS file;
you have added everything to the user documentation:
- [x] any new CMake configuration option;
- [x] any change in the yaml config;
- [x] any change to the public or plugin API;
- [x] any other new or changed user-facing feature;
- [x] any change to the dependencies;
you have correctly linked your MR to one or more issues:
- [x] your MR solves an identified issue;
- [x] your commit contain the Fix #issue keyword to autoclose the issue when merged;
[x] you have added to this file any other check that was missing.