[chore][config/configgrpc] Enable goleak check (#9217)

**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.-->
Enables goleak to run on the configgrpc package. Requires ignoring the
opencensus-go leak.

A few tests required an additional client connection close command to
exit the client go routine. Additional information can be found
[here](https://pkg.go.dev/google.golang.org/grpc#DialContext) in the
explanation for the method grpc.DialContext, specifically this comment:
```
Users should call ClientConn.Close to terminate all the pending operations after this function returns.
```
configgrpc's method
[`ToClientConn`](https://github.com/open-telemetry/opentelemetry-collector/blob/36730599ae4fb2ffc05d8e6e8a42e0bb0880703f/config/configgrpc/configgrpc.go#L178)
is directly calling the `grpc.DialContext` method referenced.

**Link to tracking Issue:** <Issue number if applicable>
#9165 

**Testing:** <Describe what testing was performed and which tests were
added.>
Added goleak check is passing

config/configgrpc/configgrpc_test.go

@@ -638,6 +638,7 @@ func TestHttpReception(t *testing.T) {
 			}
 			grpcClientConn, errClient := gcs.ToClientConn(context.Background(), componenttest.NewNopHost(), tt.TelemetrySettings())
 			assert.NoError(t, errClient)
+			defer func() { assert.NoError(t, grpcClientConn.Close()) }()
 			c := ptraceotlp.NewGRPCClient(grpcClientConn)
 			ctx, cancelFunc := context.WithTimeout(context.Background(), 2*time.Second)
 			resp, errResp := c.Export(ctx, ptraceotlp.NewExportRequest(), grpc.WaitForReady(true))
@@ -686,6 +687,7 @@ func TestReceiveOnUnixDomainSocket(t *testing.T) {
 	}
 	grpcClientConn, errClient := gcs.ToClientConn(context.Background(), componenttest.NewNopHost(), tt.TelemetrySettings())
 	assert.NoError(t, errClient)
+	defer func() { assert.NoError(t, grpcClientConn.Close()) }()
 	c := ptraceotlp.NewGRPCClient(grpcClientConn)
 	ctx, cancelFunc := context.WithTimeout(context.Background(), 2*time.Second)
 	resp, errResp := c.Export(ctx, ptraceotlp.NewExportRequest(), grpc.WaitForReady(true))
@@ -894,6 +896,7 @@ func TestClientInfoInterceptors(t *testing.T) {
 
 				grpcClientConn, errClient := gcs.ToClientConn(context.Background(), componenttest.NewNopHost(), tt.TelemetrySettings())
 				require.NoError(t, errClient)
+				defer func() { assert.NoError(t, grpcClientConn.Close()) }()
 
 				cl := ptraceotlp.NewGRPCClient(grpcClientConn)
 				ctx, cancelFunc := context.WithTimeout(context.Background(), 2*time.Second)

config/configgrpc/go.mod

@@ -17,6 +17,7 @@ require (
 	go.opentelemetry.io/collector/pdata v1.0.1
 	go.opentelemetry.io/contrib/instrumentation/google.golang.org/grpc/otelgrpc v0.47.0
 	go.opentelemetry.io/otel v1.22.0
+	go.uber.org/goleak v1.3.0
 	go.uber.org/zap v1.26.0
 	google.golang.org/grpc v1.61.0
 )

config/configgrpc/package_test.go

@@ -0,0 +1,17 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+package configgrpc
+
+import (
+	"testing"
+
+	"go.uber.org/goleak"
+)
+
+// The IgnoreTopFunction call prevents catching the leak generated by opencensus
+// defaultWorker.Start which at this time is part of the package's init call.
+// See https://github.com/open-telemetry/opentelemetry-collector/issues/9165#issuecomment-1874836336 for more context.
+func TestMain(m *testing.M) {
+	goleak.VerifyTestMain(m, goleak.IgnoreTopFunction("go.opencensus.io/stats/view.(*worker).start"))
+}