Declare where frequently used arguments for Maestro Jobs should be stored

[pawiecz]

Many Maestro Jobs definitions are Jinja2 templates that are rendered before being submitted to a relevant Runtime. They can be adjusted by setting arguments in e.g.

1. pipeline.yaml configuration file, section: jobs: $JOB: params: $PARAM: $ARG
2. template: {%- set $PARAM = '$ARG' %}

One of the recent PRs dropped the template approach if the only parameter changed was the test_method. After merging #705 there might be a need to reuse this approach for Tast/Fluster jobs as well.

There was an attempt to do so in one of the revisions of #705 but it was eventually reverted (templates can have only a single {% extends %}, other common sections could use e.g. {% includes %}).