chore(operator): Use SSA throughout runtime framework

[astefanutti]

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in Fixes #<issue number>, #<issue number>, ... format, will close the issue(s) when PR gets merged):

Fixes #2515

Depends on kubernetes-sigs/scheduler-plugins#933.

Checklist:

• Docs included if any changes are user facing

[google-oss-prow]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by:
Once this PR has been reviewed and has the lgtm label, please ask for approval from astefanutti. For more information see the Kubernetes Code Review Process.

The full list of commands accepted by this bot can be found here.

Needs approval from an approver in each of these files:

• OWNERS

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[coveralls]

Pull Request Test Coverage Report for Build 18227341710

Details

• 8 of 35 (22.86%) changed or added relevant lines in 7 files are covered.
• 2 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.2%) to 55.01%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/controller/trainjob_controller.go	0	1	0.0%
pkg/runtime/framework/plugins/jobset/jobset.go	0	26	0.0%

Files with Coverage Reduction	New Missed Lines	%
pkg/runtime/core/trainingruntime.go	2	66.01%

Totals
Change from base Build 18223898761:	-0.2%
Covered Lines:	1065
Relevant Lines:	1936

---

💛 - Coveralls