Add support for backendref service appProtocol #13482

Job	Run time
Checks and variables	1m 49s
NJS Unit Tests	12s
Unit Tests	1m 18s
Build Binary	30s
Build Plus images / build	1m 14s
Build OSS images (ngf, linux/arm64, linux/amd64) / build	1m 11s
Build OSS images (nginx, linux/arm64, linux/amd64) / build	1m 15s
Helm Tests	0s
Conformance tests (nginx, v1.33.1, false) / Run Tests	7m 28s
Conformance tests (plus, v1.33.1, true) / Run Tests	8m 39s
Conformance tests (nginx, v1.25.16, true) / Run Tests	9m 4s
Conformance tests (plus, v1.25.16, false) / Run Tests	9m 18s
Conformance tests (plus, v1.25.16, true) / Run Tests	9m 10s
Conformance tests (nginx, v1.33.1, true) / Run Tests	7m 38s
Conformance tests (plus, v1.33.1, false) / Run Tests	9m 11s
Functional tests (nginx, v1.33.1) / Run Tests	15m 7s
Functional tests (plus, v1.33.1) / Run Tests	14m 33s
Functional tests (plus, v1.25.16) / Run Tests	14m 40s
Conformance tests (nginx, v1.25.16, false) / Run Tests	8m 52s
Functional tests (nginx, v1.25.16) / Run Tests	16m 54s
Package and Publish Helm Chart	0s
	2h 18m 3s

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