[chore] [receiver/elasticsearch] Use NewDefaultClientConfig instead of manual initialization (open-telemetry#35509)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->

Similar to
open-telemetry#35452
but for the `elasticsearch` receiver.

**Link to tracking Issue:** <Issue number if applicable>
open-telemetry#35457

**Testing:** <Describe what testing was performed and which tests were
added.>

**Documentation:** <Describe the documentation added.>

Author: rogercoll

receiver/elasticsearchreceiver/config_test.go

@@ -4,6 +4,7 @@
 package elasticsearchreceiver
 
 import (
+	"net/http"
 	"path/filepath"
 	"testing"
 	"time"
@@ -14,6 +15,7 @@ import (
 	"github.com/stretchr/testify/require"
 	"go.opentelemetry.io/collector/component"
 	"go.opentelemetry.io/collector/config/confighttp"
+	"go.opentelemetry.io/collector/config/configopaque"
 	"go.opentelemetry.io/collector/confmap/confmaptest"
 	"go.opentelemetry.io/collector/receiver/scraperhelper"
 
@@ -138,6 +140,11 @@ func TestValidateEndpoint(t *testing.T) {
 }
 
 func TestLoadConfig(t *testing.T) {
+	defaultMaxIdleConns := http.DefaultTransport.(*http.Transport).MaxIdleConns
+	defaultMaxIdleConnsPerHost := http.DefaultTransport.(*http.Transport).MaxIdleConnsPerHost
+	defaultMaxConnsPerHost := http.DefaultTransport.(*http.Transport).MaxConnsPerHost
+	defaultIdleConnTimeout := http.DefaultTransport.(*http.Transport).IdleConnTimeout
+
 	t.Parallel()
 
 	cm, err := confmaptest.LoadConf(filepath.Join("testdata", "config.yaml"))
@@ -167,8 +174,13 @@ func TestLoadConfig(t *testing.T) {
 				Username:             "otel",
 				Password:             "password",
 				ClientConfig: confighttp.ClientConfig{
-					Timeout:  10000000000,
-					Endpoint: "http://example.com:9200",
+					Timeout:             10000000000,
+					Endpoint:            "http://example.com:9200",
+					Headers:             map[string]configopaque.String{},
+					MaxIdleConns:        &defaultMaxIdleConns,
+					MaxIdleConnsPerHost: &defaultMaxIdleConnsPerHost,
+					MaxConnsPerHost:     &defaultMaxConnsPerHost,
+					IdleConnTimeout:     &defaultIdleConnTimeout,
 				},
 			},
 		},

receiver/elasticsearchreceiver/factory.go

@@ -35,12 +35,13 @@ func createDefaultConfig() component.Config {
 	cfg := scraperhelper.NewDefaultControllerConfig()
 	cfg.CollectionInterval = defaultCollectionInterval
 
+	clientConfig := confighttp.NewDefaultClientConfig()
+	clientConfig.Endpoint = defaultEndpoint
+	clientConfig.Timeout = defaultHTTPClientTimeout
+
 	return &Config{
-		ControllerConfig: cfg,
-		ClientConfig: confighttp.ClientConfig{
-			Endpoint: defaultEndpoint,
-			Timeout:  defaultHTTPClientTimeout,
-		},
+		ControllerConfig:     cfg,
+		ClientConfig:         clientConfig,
 		MetricsBuilderConfig: metadata.DefaultMetricsBuilderConfig(),
 		Nodes:                []string{"_all"},
 		Indices:              []string{"_all"},