Enable blocking SAST scans in OpenShift CI

As an OpenShift developer, I want to know that my code is as secure as possible by running static analysis on each PR. Additionally, I want this to gate my ability to merge a PR.

Most of the background and reason for this is in https://issues.redhat.com/browse/MCO-998, this card primarily concerns itself with switching this configuration from non-gating to gating.

Done When:

• The configuration in the openshift/release repository is switched from non-gating to gating by setting optional: true.
• Remediate any deficiencies identified by the scans and/or an override in the form of a .snyk file placed in the MCO repository root. See: https://docs.ci.openshift.org/docs/how-tos/add-security-scanning/ for additional info about the .snyk file.