Move CI job config entries from legacy to new config
## What does this MR do?
This MR extracts jobs configuration logic from legacy CI config processor to the new code.
## What are the relevant issue numbers?
#15060
## Does this MR meet the acceptance criteria?
- Tests
- [x] Added for this feature/bug
- [x] All builds are passing
- [x] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
- [x] Branch has no merge conflicts with `master` (if you do - rebase it please)
See merge request !5087