Move stable job definition to stable-jobs.yaml

We have many job definition version for stable and master
gate and those are in same file integrated-gate.yaml. This
create confusion while modifying these jobs for master and
can end up modifying stable version.

Example: https://review.opendev.org/c/openstack/tempest/+/794312

Keeping all stable job definition in stable-jobs.yaml will help
us to accidentally modifying the stable jobs definition.

Change-Id: I44ae4a4b7070dd44f50070ad24e9d33f417ae955
2 files changed