backendHTTPRouteIndexFunc() is not adding indexer when Backend kind is ServiceImport

[muwaqar]

Description:
The backendHTTPRouteIndexFunc() in the Kubernetes controller is NOT adding field indexer for when Backend kind is ServiceImport.

for _, backend := range rule.BackendRefs {
	if backend.Kind == nil || string(*backend.Kind) == resource.KindService || string(*backend.Kind) == egv1a1.KindBackend {
		...
	}
}

source:

gateway/internal/provider/kubernetes/indexers.go

Line 114 in c492089

if backend.Kind == nil || string(*backend.Kind) == resource.KindService || string(*backend.Kind) == egv1a1.KindBackend {

Repro steps:
N/A

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Environment:

Include the environment like gateway version, envoy version and so on.

Logs:

Include the access logs and the Envoy logs.