[UX2.0] Adds the remaining Transport WAN/VPN/Interfaces

[seconroy]

Description

Add the remaining Transport WAN/VPN/Interfaces:

• transport/wan/vpn/interface/gre
• transport/wan/vpn/interface/ipsec
• transport/wan/vpn/interface/serial
• transport/wan/vpn/interface/cellular

Types of Changes

• [x] New feature (non-breaking change which adds functionaality)
• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)
• [ ] Build/CI change
• [ ] Code quality improvement/refactoring/documentation (no functional changes)

Checklist

• [x] My code follows the code style of this project
• [x] I have added tests to cover my changes
• [x] All new and existing tests pass locally