[ENHANCEMENT] Logging eagerly serializes each condition on every feature flag evaluation

Description

BaseCondition.ToString() serializes on every log-message construction (BaseCondition.cs):

public override string ToString() => JsonConvert.SerializeObject(this, Formatting.None);

It's used inside interpolated strings like $@"Audience condition {this} evaluated to UNKNOWN...", which C# evaluates eagerly before logger.Log(LogLevel.DEBUG, ...) is called. So even with logging disabled, you pay a JsonConvert.SerializeObject per condition on many paths (Evaluate, ExactEvaluator, NumberEvaluator, SubstringEvaluator, ...). This is a real hot-path cost.

Consider gating the log calls behind a level check so the interpolation doesn't run, or cache the serialized condition.

Benefits

Less allocations and resource utilization and feature flags can be used in hot paths.

Detail

No response

Examples

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Risks/Downsides

No response

Start with OptimizelySDK/AudienceConditions/BaseCondition.cs and inspect the logging paths in Evaluate, ExactEvaluator, NumberEvaluator, and SubstringEvaluator. Trace how interpolated messages reach logger.Log when debug logging is disabled, then verify that condition serialization is avoided or reused without changing the logged messages or evaluation behavior.