It's useful for some tests to use.

so that we can simulate running at a later time, to check backups, crontabs etc

Using an script to set the environment is easier to use, but the main
reason is that if we want to be able to use shared part from outer
slapos (like when using in theia or slaprunner), the working directory
for test must be contained in the instance directory of the outer
slapos, so that when we run slapos node prune in the outer slapos this
command can see that shared parts are used.

QUIC is not used at all, and became superseded by HTTP/3

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.

Those values are free to be used by tests in order to obtain working
IPv4 and IPv6 addresses or other parameters fetched during test node
instantiation.

Note that old-style keys (like LOCAL_IPV4 and LOCAL_IPV6) are kept for
backward compatibility.

/reviewed-on nexedi/slapos!471

Problem has been found, and as this mode emits a lot of data with test result
disable it.

It will allow to track behaviour of the test on various test nodes.

For supervisord AF_UNIX socket

This is a convention from
http://community.slapos.org/slapos_community/wiki/slapos-Wiki.Home/developer-SlapOS.Conventions.Guidelines

To run tests from software/proftpd/test