Add Security to Dev Escalation

Why is this change being made?

This change adds the ability for Security Dept. to raise S1/P1 vulnerabilities which are being actively exploited or at high risk of being exploited on GitLab.com and may impact many or all customer data.

Does this MR meet the acceptance criteria?

Conformity

• Added description to this MR explaining the reasons for proposed change, per say-why-not-just-what