(backport) feat: add configurable replicas and antiaffinity to gateway deployment #1216

Job	Run time
Publish Charm / Generate the Charm Matrix	6s
Run Tests / Lint Code (pilot)	24s
Run Tests / Integration Test (1.27-strict/stable, integration)	44m 23s
Run Tests / Lint Code (gateway)	22s
Run Tests / Unit Test (pilot)	37s
Run Tests / Integration Test (1.27-strict/stable, integration-tls-provider)	37m 28s
Run Tests / Unit Test (gateway)	35s
Run Tests / Integration Test (1.27-strict/stable, integration-tls-secret)	37m 27s
Run Tests / Observability Integration Test (1.25-strict/stable)	35m 49s
Run Tests / Integration Test (1.30-strict/stable, integration)	41m 58s
Run Tests / Observability Integration Test (1.26-strict/stable)	36m 10s
Run Tests / Integration Test (1.30-strict/stable, integration-tls-provider)	37m 16s
Run Tests / Integration Test (1.30-strict/stable, integration-tls-secret)	36m 42s
Run Tests / Check libraries (istio-gateway) / Check libraries	37s
Run Tests / Check libraries (istio-gateway) / Lint	8s
Run Tests / Check libraries (istio-pilot) / Lint	11s
Run Tests / Check libraries (istio-pilot) / Check libraries	29s
Run Tests / Terraform (gateway) / Lint Terraform	10s
Run Tests / Terraform (pilot) / Lint Terraform	8s
Run Tests / Terraform (gateway) / Apply / Apply Terraform	5m 37s
Run Tests / Terraform (gateway) / Check / Check Terraform	5s
Run Tests / Terraform (pilot) / Apply / Apply Terraform	5m 18s
Run Tests / Terraform (pilot) / Check / Check Terraform	6s
Publish Charm / Publish Charm (./charms/istio-gateway)	13m 14s
Publish Charm / Publish Charm (./charms/istio-pilot)	17m 20s
	5h 52m 40s

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