Add port names to agent service

[khewonc]

What does this PR do?

Add port names to the agent service.

Motivation

When enabling both dogstatsd and APM, the agent service tries to expose 2 unnamed ports, which is not allowed by Kubernetes as it is considered ambiguous. The operator logs give the following error:

{"level":"ERROR","ts":"2022-04-11T02:23:42Z","logger":"controller-runtime.manager.controller.datadogagent","msg":"Reconciler error","reconciler group":"datadoghq.com","reconciler kind":"DatadogAgent","name":"datadog","namespace":"default","error":"Service \"datadog-agent\" is invalid: [spec.ports[0].name: Required value, spec.ports[1].name: Required value]"}

Describe your test plan

Spin up a DatadogAgent with APM enabled in the agent spec (agent.apm.enabled=true) so that both dogstatsd and APM are enabled:

spec:
  agent:
    apm:
      enabled: true

If needed, to force creation of the agent service in Kubernetes v1.21+, enable agent.localService.forceLocalServiceEnable=true:

spec:
  agent:
    localService:
      forceLocalServiceEnable: true

There shouldn't be any error in the operator logs about creating the agent service. The service should be created exposing both dogstatsd and APM ports:

> kubectl describe svc 
NAME                                   TYPE        CLUSTER-IP     EXTERNAL-IP   PORT(S)             AGE
datadog-agent                          ClusterIP   <cluster-ip>   <none>        8125/UDP,8126/TCP   2d19h