Add structured reporting diff to ComputeTargetTCPProxy (#6755)

### BRIEF Change description

Fixes #6559

#### WHY do we need this change?

Add structured reporting diff to the controller in
`pkg/controller/direct/compute/targettcpproxy_controller.go`.
The `structuredreporting.ReportDiff` should be used in the `Update`
method of the adapter to report which fields are being updated.
This helps in debugging reconciliation loops and provides better
visibility into what changed.

#### Special notes for your reviewer:

#### Does this PR add something which needs to be 'release noted'?
```release-note
NONE
```

#### Additional documentation e.g., references, usage docs, etc.:
```docs
NONE
```

#### Intended Milestone
- [ ] Reviewer tagged PR with the actual milestone.

### Tests you have done

- [ ] Run `make ready-pr` to ensure this PR is ready for review.
- [ ] Perform necessary E2E testing for changed resources.

Author: cheftako

pkg/controller/direct/compute/targettcpproxy_controller.go

@@ -29,6 +29,7 @@ import (
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct"
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct/directbase"
 	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/controller/direct/registry"
+	"github.com/GoogleCloudPlatform/k8s-config-connector/pkg/structuredreporting"
 	"k8s.io/apimachinery/pkg/apis/meta/v1/unstructured"
 	"k8s.io/apimachinery/pkg/runtime"
 	"k8s.io/klog/v2"
@@ -241,6 +242,12 @@ func (a *targetTCPProxyAdapter) Update(ctx context.Context, updateOp *directbase
 		// Even though there is no update, we still want to update KRM status
 		updated = a.actual
 	} else {
+		report := &structuredreporting.Diff{Object: updateOp.GetUnstructured()}
+		for path := range paths {
+			report.AddField(path, nil, nil)
+		}
+		structuredreporting.ReportDiff(ctx, report)
+
 		// Changes on resource spec are detected
 		if parent.Location != "global" {
 			// Regional ComputeTargetTCPProxy API does not support Update