Add validation in the latticeServiceModelBuildTask: the `hostnames` in the TLSRoute is required field for the aws gateway api controller supported TLSRoute

[Zijun Wang]

Due to the VPC lattice Considerations:

The VPC Lattice service must have a custom domain name.

For aws gateway api controller supported TLSRoute, it must have at least one item in the hostnames field.

https://docs.aws.amazon.com/vpc-lattice/latest/ug/tls-listeners.html#tls-listeners-considerations

Need to change code here:

aws-application-networking-k8s/pkg/gateway/model_build_lattice_service.go

Line 135 in 036e2a3

 spec.CustomerDomainName = string(t.route.Spec().Hostnames()[0])