KPET-DB: Support reserving systems
@huanian Li has [expressed|https://projects.engineering.redhat.com/browse/FASTMOVING-1916?focusedCommentId=2509058&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-2509058] the need to reserve systems targeted by tests, the same way kpet normally would, to simplify test development.
We can support this by adding another "variable" in kpet-db. We can call it "{{reservesys_duration}}", and set its default to zero. Then when it's specified non-zero we can add the reservesys element with the specified duration to every recipe in the output. It would then be up to the user to combine this with the new "{{--tests}}" option.
E.g.:
kpet run generate -a x86_64 -k "KERNEL" -t rhel82-z --tests 'xfstests.*' -v reservesys_duration=259200
This change could be done entirely in kpet-db.
JIRA ticket created by @nkondras