Exclude custom events from Application Insights sampling

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Background on sampling: https://learn.microsoft.com/en-us/azure/azure-monitor/app/sampling

Example from Nova.SearchAlgorithm: https://github.com/Anthony-Nolan/Nova.SearchAlgorithm/blob/865d65fd8775a033be3fb39c32c26be9a3bb1971/temp/ApplicationInsights.config#L93

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Testing

• Data refresh run before and after release of Atlas v1.4.2 to uat-atlas env.
• Before: 136 HLA failures reported via alerts, but only 2 custom events logged to AI.
• After: 136 HLA failures reported via alerts, and 136 logged as events to AI.

Conclusion, custom events are no longer being sampled during periods of high logging activity. ✅

Testing Passed