fix(conformance-test): HTTPRouteRewriteHost

[AlinsRan]

Type of change:

• Bugfix
• New feature provided
• Improve performance
• Backport patches
• Documentation
• Refactor
• Chore
• CI/CD or Tests

What this PR does / why we need it:

The RewriteConfig plugin will be shared by multiple filters, resulting in headers not being initialized and causing panic.

{"controller": "httproute", "controllerGroup": "gateway.networking.k8s.io", "controllerKind": "HTTPRoute", "HTTPRoute": {"name":"rewrite-host","namespace":"gateway-conformance-infra"}, "namespace": "gateway-conformance-infra", "name": "rewrite-host", "reconcileID": "7f56d988-738f-4f3c-b697-dc8c8c8119bd", "panic": "runtime error: invalid memory address or nil pointer dereference", "panicGoValue": "\"invalid memory address or nil pointer dereference\"", "stacktrace": "goroutine 998 [running]:
k8s.io/apimachinery/pkg/util/runtime.logPanic({0x254dcf8, 0xc000ef3ad0}, {0x1e93ea0, 0x378c500})
    /Users/rong/go/pkg/mod/k8s.io/[email protected]/pkg/util/runtime/runtime.go:107 +0xbc
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).Reconcile.func1()
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:108 +0x112
panic({0x1e93ea0?, 0x378c500?})
    /usr/local/Cellar/go/1.24.5/libexec/src/runtime/panic.go:792 +0x132
github.com/apache/apisix-ingress-controller/internal/adc/translator.(*Translator).fillPluginFromHTTPRequestHeaderFilter(0x8?, 0xc000e3a690, 0xc0001ca050)
    /Users/rong/workspace/apisix-ingress-controller/internal/adc/translator/httproute.go:194 +0x232
github.com/apache/apisix-ingress-controller/internal/adc/translator.(*Translator).fillPluginsFromHTTPRouteFilters(0xc00000f488, 0xc000e3a690, {0xc0011a60e0, 0x19}, {0xc0009f18c0?, 0xc00063fe88?, 0xc00063fe88?}, {0xc000459dc0, 0x1, 0x1}, ...)
    /Users/rong/workspace/apisix-ingress-controller/internal/adc/translator/httproute.go:51 +0x451
github.com/apache/apisix-ingress-controller/internal/adc/translator.(*Translator).TranslateHTTPRoute(0xc00000f488, 0xc000e12240, 0xc000da9980)
    /Users/rong/workspace/apisix-ingress-controller/internal/adc/translator/httproute.go:638 +0x978
github.com/apache/apisix-ingress-controller/internal/provider/apisix.(*apisixProvider).Update(0xc000749e60, {0xc0007d81e0?, 0x19?}, 0xc000e12240, {0x25769e8, 0xc000da9680})
    /Users/rong/workspace/apisix-ingress-controller/internal/provider/apisix/provider.go:111 +0xe97
github.com/apache/apisix-ingress-controller/internal/controller.(*HTTPRouteReconciler).Reconcile(0xc0004a3110, {0x254dcf8, 0xc000ef3ad0}, {{{0xc001098f80?, 0x21c9778?}, {0xc000d723c0?, 0x100?}}})
    /Users/rong/workspace/apisix-ingress-controller/internal/controller/httproute_controller.go:254 +0x15bb
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).Reconcile(0xc000ef3a40?, {0x254dcf8?, 0xc000ef3ad0?}, {{{0xc001098f80?, 0x0?}, {0xc000d723c0?, 0x0?}}})
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:119 +0xbf
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).reconcileHandler(0x25716c0, {0x254dd30, 0xc0005e4910}, {{{0xc001098f80, 0x19}, {0xc000d723c0, 0xc}}}, 0x0)
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:334 +0x3ad
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).processNextWorkItem(0x25716c0, {0x254dd30, 0xc0005e4910})
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:294 +0x21b
sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).Start.func2.2()
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:255 +0x85
created by sigs.k8s.io/controller-runtime/pkg/internal/controller.(*Controller[...]).Start.func2 in goroutine 358
    /Users/rong/go/pkg/mod/sigs.k8s.io/[email protected]/pkg/internal/controller/controller.go:251 +0x6b5
"}

Pre-submission checklist:

• Did you explain what problem does this PR solve? Or what new features have been added?
• Have you added corresponding test cases?
• Have you modified the corresponding document?
• Is this PR backward compatible? If it is not backward compatible, please discuss on the mailing list first

[ronething]

lgtm