The test system requires to adapt to changes in slapos.core rapidly,
and so it has use the most recent version.

needed for slapos.testing

  Remove duplicated version definition at software level to prevent excessive duplication
  of the value.

Tests need to open xz files for checking.

Usually the slapos.core on nodes is installed with slapos.libnetworkcache,
so do the same for testing environment, so shacache can be used during
installation.

Improved supervisord management is critical for maintenance of instances
between tests.

Since slapos.core 1.4.16+ slapos proxy is not able to consume or publish
non-strings, which makes tests not working.

They are dependencies of slapos.toolbox and we already agreed to put slapos.toolbox version in a shared file.

/cc @jerome @jm

/reviewed-on nexedi/slapos!502

Since some software releases have unit tests, it is good idea to run the
tests for each commit on slapos branch.

This SR follow slapos-testing SR in a way how tests are grouped and run.

Fixed erp5.util is used to expose good test suite names.