Emit multiline telemetry from DaemonSet heartbeat

Adds multilineEnabled and multilineLanguages dimensions to the
ContainerLogDaemonSetHeartbeatEvent in source/plugins/go/src/telemetry.go.

Previously the multiline telemetry was emitted only from the cAdvisor
heartbeat in either CAdvisorMetricsAPIClient.rb (requires fluentd) or
cadvisor.go (requires AZMON_RESOURCE_OPTIMIZATION_ENABLED=true). In
LOGS_AND_EVENTS_ONLY mode neither emitter runs, so the multiline
configuration was never reported in telemetry for that profile.

The DaemonSet heartbeat is the only telemetry path that always runs in
this mode (it already carries the logsAndEventsOnly dimension), making
it the right place to surface the multiline configuration.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: suyadav1

source/plugins/go/src/telemetry.go

@@ -295,6 +295,15 @@ func SendContainerLogPluginMetrics(telemetryPushIntervalProperty string) {
 					telemetryDimensions["logsAndEventsOnly"] = logsAndEventsOnly
 				}
 
+				azmonMultilineEnabled := os.Getenv("AZMON_MULTILINE_ENABLED")
+				if azmonMultilineEnabled != "" {
+					telemetryDimensions["multilineEnabled"] = azmonMultilineEnabled
+					azmonMultilineLanguages := os.Getenv("AZMON_MULTILINE_LANGUAGES")
+					if azmonMultilineLanguages != "" {
+						telemetryDimensions["multilineLanguages"] = azmonMultilineLanguages
+					}
+				}
+
 				isHighLogScaleMode := os.Getenv("IS_HIGH_LOG_SCALE_MODE")
 				if isHighLogScaleMode != "" {
 					telemetryDimensions["isHighLogScaleMode"] = isHighLogScaleMode