Bypass load balancer during feature flag checks

What does this MR do and why?

Bypasses the load balancer during feature flag checks. This will allow safe use of feature flags inside the load balancer, so that the load balancer can be more easily iterated on. Without this change, calling Feature.enabled? in the load balancer would cause a recursive loop if the feature flag was not cached.

Feature flags already use a two-layer caching system, first a 60 second request-local in-memory cache, and second a 1-hour ttl redis cache. So primary load from this change will be roughly 1 query per feature flag per hour.

See #430002 for context.

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