Problem: Multiple tests failing in Prow CI because curl commands don't work in Windows PowerShell containers.

Affected Tests:
- OCP-39451: Windows_Containers Access Windows workload through clusterIP
- OCP-31276: Windows_Containers CNI and internal networking
- OCP-28632: Windows_Containers Windows and Linux east west network

Root Cause:
curl is not available or doesn't work properly in Windows PowerShell (nanoserver) containers

Solution:
Replace all curl commands with PowerShell's native Invoke-WebRequest

Files Modified:
- test/extended/winc/winc.go (OCP-39451, OCP-31276, OCP-28632)