[Spike] Investigate why events (Span, Transaction) aren't reported when all timeslice metrics are dropped

We had a report from a customer who added a global admin Metric Normalization Rule to ignore all metrics (i.e. ^.*$). An unexpected consequence was that all telemetry ceased reporting for all entities in the account, including event data such as Transaction and Span events. It's unclear why this occurred and whether it is intentional, or if there is an underlying bug that should be resolved.

Make sure to do all testing in a US Prod account as the behavior will differ in staging (due to a feature flag that is not deployed in staging).

For additional context, see these links:

• https://new-relic.atlassian.net/browse/NR-592241
• https://newrelic.slack.com/archives/C0NUYPJKA/p1784157410459239
• https://newrelic.slack.com/archives/C0NUYPJKA/p1784189519877609

The goal of this story is to gain an understanding of how metric normalization rules could affect events and determine if this is a bug or not. Additionally, update the Metric Normalization Rule documentation that states "metric normalization applies only to metric timeslice data" to reflect how other data types may be impacted.

Metric normalization rules help you to manage Metric Grouping Issues (MGIs). This helps to ensure that application performance data remains relevant. The metric normalization applies only to metric timeslice data.