docs: Add Q&A section for ingress controller

[Revolyssup]

Current State

All the tutorials install Apisix with service type NodePort and access APISIX either by nodeport or by curl'ing into the Pod. Users might have questions like how can APISIX be exposed as service type LoadBalancer? and how can the Ingress resource be allocated Address?

Desired State

Answer these questions in the Q&A section on installing APISIX with ingress.

[Revolyssup]

@tao12345666333 Can I add these qa to existing FAQ here ? https://apisix.apache.org/docs/ingress-controller/FAQ/

[tao12345666333]

Sure!

[Revolyssup]

Completed #1907