convert DeviceShifuBase data structure from single EdgeDevice to a list type of EdgeDevice

Change EdgeDevice type from single type to array type, only support first item of config so not breaking current behavior.

Accept criteria:

1. in examples/httpDeviceShifu/deployment/http-edgedevice.yaml, let's config as following
```
spec:
-sku: "device1"
connection: Ethernet
address: 192.168.11.16:12345
protocol: HTTP
```
2. after this change, make shifu still working with following command
```
kubectl apply -f examples/httpDeviceShifu/deployment
```

3. if there are multiple edgedevices in http_edgedevice.yaml file, always use the first one and ignore others

Start with examples/httpDeviceShifu/deployment/http-edgedevice.yaml, then run kubectl apply -f examples/httpDeviceShifu/deployment to observe the current behavior. Done means the configuration uses a list of EdgeDevice entries, the command still works, and when multiple entries are present only the first is used.

Written by the indexing model from the issue text.