docs: testing: Adjust the docs on how to run container workloads locally

docs: testing: Adjust the docs on how to run container workloads locally

The fact that we need ci/helper script to run the workloads remains
true, but the invocation has changed as of commit
eb41e456309dbea5b8b9f647f953ad98985ec1fe . We also extracted GitLab job
specs into a standalone ci/jobs.sh script which allows execution of any
container job we run in upstream CI locally, unlike the original
functionality which only allowed builds, tests and shell (although
important to say it could be adjusted with the right meson/ninja args).

lcitool also became mandatory as it enables the container execution
which replaced a Makefile we used to have for this purpose.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Pavel Hrdina <phrdina@redhat.com>