Fission meets OpenTelemetry (#2157)

* add opentracing section and otelCollectorEndpoint
* initialize OTLP exporter
* pkg/controller: changes for context propagation
* pkg/executor: changes for context propagation
* pkg/fetcher: changes for context propagation
* pkg/router: changes for context propagation
* pkg/storagesvc: changes for context propagation
* set no default value for otel collector endpoint
* update readme and add notes to charts
* move common code to pkg/utils/otel
* adding fn and env as attributes
* don't use otelhttp transport for websocket
* URL ignore with common filter UrlsToIgnore

Note: The web socket example does not work when using OTEL HTTP. Here is an issue related to that on open-telemetry/opentelemetry-js-contrib.

Signed-off-by: Gaurav Gahlot <gauravgahlot0107@gmail.com>
Co-authored-by: Sanket Sudake <sanketsudake@gmail.com>

pkg/fetcher/config/config.go

@@ -282,6 +282,16 @@ func (cfg *Config) addFetcherToPodSpecWithCommand(podSpec *apiv1.PodSpec, mainCo
 				},
 			},
 		},
+		Env: []apiv1.EnvVar{
+			{
+				Name:  "OPENTRACING_ENABLED",
+				Value: os.Getenv("OPENTRACING_ENABLED"),
+			},
+			{
+				Name:  "OTEL_COLLECTOR_ENDPOINT",
+				Value: os.Getenv("OTEL_COLLECTOR_ENDPOINT"),
+			},
+		},
 	}
 
 	// Pod is removed from endpoints list for service when it's