Add experimentation circuit breaker

What does this MR do and why?

Adds an ops feature flag that will enable us to turn off all GLEX experimentation on .com.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #353921 (closed)