[exporter/datadogexporter] Add example for host metadata (open-telemetry#31604)

**Description:** 
Adds example `host-metadata.yaml` that demonstrates use of [Mapping
OpenTelemetry Semantic Conventions to Infrastructure List Host
Information](https://docs.datadoghq.com/opentelemetry/schema_semantics/host_metadata)
with the exporter and connector.

Author: liustanley

connector/datadogconnector/go.mod

@@ -266,3 +266,5 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/k8sa
 replace github.com/open-telemetry/opentelemetry-collector-contrib/extension/storage => ../../extension/storage
 
 replace github.com/openshift/api v3.9.0+incompatible => github.com/openshift/api v0.0.0-20180801171038-322a19404e37
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor => ../../processor/transformprocessor

exporter/datadogexporter/examples/host-metadata.yaml

@@ -0,0 +1,43 @@
+receivers:
+  otlp:
+    protocols:
+      http:
+        endpoint: "localhost:4318"
+      grpc:
+        endpoint: "localhost:4317"
+processors:
+  probabilistic_sampler:
+    sampling_percentage: 20
+  batch:
+    send_batch_max_size: 1000
+    send_batch_size: 100
+    timeout: 10s
+  transform:
+    metric_statements:
+      - context: resource
+        statements:
+          - set(attributes["datadog.host.use_as_metadata"], true)
+    trace_statements:
+      - context: resource
+        statements:
+          - set(attributes["datadog.host.use_as_metadata"], true)
+connectors:
+    datadog/connector:
+exporters:
+  datadog:
+    api:
+      key: ${env:DD_API_KEY}
+service:
+  pipelines:
+    traces:
+      receivers: [otlp]
+      processors: [batch, transform]
+      exporters: [datadog/connector]
+    traces/2:
+      receivers: [datadog/connector]
+      processors: [batch, probabilistic_sampler]
+      exporters: [datadog]
+    metrics:
+      receivers: [datadog/connector]
+      processors: [batch, transform]
+      exporters: [datadog]

exporter/datadogexporter/examples_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/k8sattributesprocessor"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/probabilisticsamplerprocessor"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/resourcedetectionprocessor"
+	"github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/dockerstatsreceiver"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/filelogreceiver"
 	"github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver"
@@ -112,6 +113,7 @@ func newTestComponents(t *testing.T) otelcol.Factories {
 			k8sattributesprocessor.NewFactory(),
 			resourcedetectionprocessor.NewFactory(),
 			probabilisticsamplerprocessor.NewFactory(),
+			transformprocessor.NewFactory(),
 		}...,
 	)
 	require.NoError(t, err)

exporter/datadogexporter/go.mod

@@ -28,6 +28,7 @@ require (
 	github.com/open-telemetry/opentelemetry-collector-contrib/processor/k8sattributesprocessor v0.96.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/processor/probabilisticsamplerprocessor v0.96.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/processor/resourcedetectionprocessor v0.96.0
+	github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor v0.96.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/dockerstatsreceiver v0.96.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/filelogreceiver v0.96.0
 	github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver v0.96.0
@@ -81,6 +82,7 @@ require (
 	github.com/DataDog/zstd v1.5.2 // indirect
 	github.com/Microsoft/go-winio v0.6.1 // indirect
 	github.com/Showmax/go-fqdn v1.0.0 // indirect
+	github.com/alecthomas/participle/v2 v2.1.1 // indirect
 	github.com/alecthomas/units v0.0.0-20211218093645-b94a6e3cc137 // indirect
 	github.com/armon/go-metrics v0.4.1 // indirect
 	github.com/beorn7/perks v1.0.1 // indirect
@@ -154,6 +156,7 @@ require (
 	github.com/hashicorp/nomad/api v0.0.0-20230721134942-515895c7690c // indirect
 	github.com/hashicorp/serf v0.10.1 // indirect
 	github.com/hetznercloud/hcloud-go/v2 v2.4.0 // indirect
+	github.com/iancoleman/strcase v0.3.0 // indirect
 	github.com/imdario/mergo v0.3.16 // indirect
 	github.com/inconshreveable/mousetrap v1.1.0 // indirect
 	github.com/ionos-cloud/sdk-go/v6 v6.1.9 // indirect
@@ -189,6 +192,7 @@ require (
 	github.com/open-telemetry/opentelemetry-collector-contrib/internal/common v0.96.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/internal/docker v0.96.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/internal/filter v0.96.0 // indirect
+	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/ottl v0.96.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/pdatautil v0.96.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/stanza v0.96.0 // indirect
 	github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator/prometheus v0.96.0 // indirect
@@ -362,3 +366,5 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/tailsamplingprocessor => ../../processor/tailsamplingprocessor
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/extension/storage => ../../extension/storage
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor => ../../processor/transformprocessor

exporter/datadogexporter/go.sum

@@ -277,3 +277,5 @@ replace github.com/open-telemetry/opentelemetry-collector-contrib/pkg/translator
 replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/probabilisticsamplerprocessor => ../../../processor/probabilisticsamplerprocessor
 
 replace github.com/open-telemetry/opentelemetry-collector-contrib/receiver/prometheusreceiver => ../../../receiver/prometheusreceiver
+
+replace github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor => ../../../processor/transformprocessor