feat: add azureopenai backend

[arbreezy]

Closes #

📑 Description

Adding azureopenai backend and introduce kubebuilder markers to assign default values for model=gpt-3.5-turbo and backend=openai
I've also added an evaluation on the backend accepted names to help users define their desired backend name

✅ Checks

• My pull request adheres to the code style of this project
• My code requires changes to the documentation
• I have updated the documentation as required
• All the tests have passed

ℹ Additional Information

There is a reconcile error if a user tries to specify engine without having azureopenai as their backend.
example:

2023-05-05T20:29:08+03:00	ERROR	Reconciler error	{"controller": "k8sgpt", "controllerGroup": "core.k8sgpt.ai", "controllerKind": "K8sGPT", "K8sGPT": {"name":"k8sgpt-sample","namespace":"kube-system"}, "namespace": "kube-system", "name": "k8sgpt-sample", "reconcileID": "5a08a085-610b-44f6-ada8-19f052aad6b3", "error": "Engine is supported only by azureopenai provider."}