[8.8] Add warning for max alerts circuit breaker (#164217) (#164423)

# Backport

This will backport the following commits from `main` to `8.8`:
- [Add warning for max alerts circuit breaker
(#164217)](#164217)

<!--- Backport version: 8.9.8 -->

### Questions ?
Please refer to the [Backport tool
documentation](https://github.com/sqren/backport)

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docs/settings/alert-action-settings.asciidoc

@@ -245,6 +245,8 @@ Specifies the maximum number of actions that a rule can generate each time detec
 
 `xpack.alerting.rules.run.alerts.max` {ess-icon}::
 Specifies the maximum number of alerts that a rule can generate each time detection checks run. Default: 1000.
++
+WARNING: The exact number of alerts your cluster can safely handle depends on your cluster configuration and workload, however setting a value higher than the default (`1000`) is not recommended or supported. Doing so could strain system resources and lead to performance issues, delays in alert processing, and potential disruptions during high alert activity periods.
 
 `xpack.alerting.rules.run.timeout` {ess-icon}::
 Specifies the default timeout for tasks associated with all types of rules.