Plugins: Pass OTEL sampling config to plugins (#76834)

* Pass OTEL sampling config to plugins

* fix capital letters

* Do not pass sampler env vars if sampling is not configured

* Add tests

* PR review feedback

* Simplify tracing env vars logic

* Update test to reflect pkg/infra/tracing behaviour

pkg/services/pluginsintegration/config/tracing.go

@@ -20,8 +20,11 @@ func newTracingCfg(grafanaCfg *setting.Cfg) (pCfg.Tracing, error) {
 	}
 	return pCfg.Tracing{
 		OpenTelemetry: pCfg.OpenTelemetryCfg{
-			Address:     ots.Address,
-			Propagation: ots.Propagation,
+			Address:          ots.Address,
+			Propagation:      ots.Propagation,
+			Sampler:          ots.Sampler,
+			SamplerParam:     ots.SamplerParam,
+			SamplerRemoteURL: ots.SamplerRemoteURL,
 		},
 	}, nil
 }