Add an example tf files to configure HA VPN tunnels

[yunkon-kim]

This PR will add tf files to configure and test HA VPN tunnels between GCP and Azure.

• Define providers, which are GCP and Azure
• Create network resources for HA VPN tunnels
• Create VM instances for ping test
• Create a security group or network security groups for instance access and testing

The result of the last tofu apply
Note - I'd like to skip the long execution history printed on the terminal.
A requirement from Azure: the subnet used to configure VPN tunnels must have the name GatewaySubnet

• Approximate elapsed time:** 25m00s (🤔 It took 20m27s to create a virtual network gateway in Azure.)

The result of the last tofu destroy

• Approximate elapsed time: 18m00s (🤔 It took 15m43s to destroy a subnet and 6m35s to destroy GatewaySubnet in Azure.)

Ping test
VM instance in GCP

VM in Azure

Test

Next plans:

1. Refactoring for the entire project #25
2. Add APIs to configure HA VPN tunnels between GCP and Azure #29
3. Configure and test HA VPN tunnels between AWS, GCP and MS Azure #10

(CC. @seokho-son, @powerkimhub)

[powerkimhub]

• 왜 이리 오래 걸리나 했는데, 빠른 편이네요

• Creation Time

• Deletion Time

[yunkon-kim]

@powerkimhub 정보를 공유해주셔서 감사합니다 🙇‍♂️

개발한 HCL이 잘못된 줄 알고서 몇 일 동안 수정과 테스트를 반복했는데 20분이 짧은 거였다니 허탈합니다 ^^;;;

(참고: 생성 중에 console 상에서 확인할 수 있는 정보가 그나마 error / updating 두 가지 정도의 상태 정보였습니다.)