[feat][doc] PIP-264: Update OpenTelemetry deployment documentation (#934

)

* Clarify OpenTelemetry resource attributes to Prometheus labels relationship

* Describe OpenTelemetry memory reuse mode in Pulsar

docs/deploy-monitoring.md

@@ -195,12 +195,7 @@ OTEL_EXPORTER_PROMETHEUS_PORT
 This endpoint must be accessible by the remote Prometheus scrape server. Note that the exporter is less resource
 efficient than the OTLP exporter.
 
-Prometheus currently exports the resource attributes in metric `target_info`. In practice, if you have more than one
-cluster, it forces you to use PromQL joins to obtain the cluster ID label.
-
-The Pulsar community has added the option to the OpenTelemetry Java SDK Prometheus Exporter to embed (copy) the cluster
-ID label (`pulsar.cluster`) to each outgoing time series labels. Once this is finalized it will be added by default into
-Pulsar.
+All OpenTelemetry resource attributes are automatically copied to Prometheus labels on each time series.
 
 For further configuration details, refer to the exporter
 [documentation](https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk-extensions/autoconfigure/README.md#prometheus-exporter).
@@ -234,3 +229,11 @@ OpenTelemetry provides an experimental mechanism to control the maximum cardinal
 limiting the resource usage of the exporter. Pulsar sets the value to 10000 attributes by default. For brokers with a
 large number of topics, this can prove insufficient. The value is controlled by environment variable
 `OTEL_EXPERIMENTAL_METRICS_CARDINALITY_LIMIT`.
+
+#### Memory Reuse Configuration
+
+OpenTelemetry provides an experimental mechanism to control the reuse of metric attributes. This is particularly useful
+for systems with high cardinality metrics, as it reduces the number of memory allocations caused by collector runs. The
+mechanism is enabled by default in Pulsar, and can be overridden by environment variable
+`OTEL_JAVA_EXPERIMENTAL_EXPORTER_MEMORY_MODE`. For further details and valid configuration values, refer to the
+exporter configuration [documentation](https://opentelemetry.io/docs/languages/java/configuration/#exporters).