feat: add dataCenterId pod create option

[jojje]

E-XXXX: add dataCenterId pod create option

Adds the ability to control the specific datacenter a pod is to be created in.

How I tested it

1. Used go debugger to ensure the graphql statement was rendered correctly.
2. Built the CLI and ran the following command: runpodctl create pod --dataCenterId EU-SE-1 --secureCloud --gpuType "NVIDIA A40" --gpuCount 1 --templateId runpod-torch-v21 --imageName runpod/pytorch:2.1.0-py3.10-cuda11.8.0-devel-ubuntu22.04 --name test
3. verified that the Pod created was indeed listed as being in the SE location using the the runpod WebUI (console): https://www.runpod.io/console/pods (and expand the pod to see the location field).

Closes #158

PS, no idea what the "E-XXXX" is supposed to be, so let me know and I'll add an appropriate number there.