Provide APIs to mange GCP to Azure VPN tunnel and test environment

[yunkon-kim]

APIs to manage GCP to Azure VPN tunnel
: It's necessary to inject existing resources (e.g., resource group, VPC, subnet, etc.).
: It's useful to create and delete GCP to Azure VPN tunnel.

APIs to manage test environment
: It's useful to make a test environment quickly.
: Currently, it can configure and delete basic cloud network resources (e.g., VPC, subnet, etc.).

Related issues: #23, #25, #29

[yunkon-kim]

google_compute_instance.vm_instance_1: Creating...
azurerm_network_interface.nic_1: Creating...
╷
│ Error: creating Network Interface (Subscription: "a20fed83-96bd-4480-92a9-140b8e3b7c3a"
│ Resource Group Name: "tofu-rg-01"
│ Network Interface Name: "nic_1_name"): performing CreateOrUpdate: unexpected status 400 with error: GatewaySubnet: Subnet with name 'GatewaySubnet' can be used only for the Gateway resource.
│
│   with azurerm_network_interface.nic_1,
│   on azure-virtual-machine.tf line 1, in resource "azurerm_network_interface" "nic_1":
│    1: resource "azurerm_network_interface" "nic_1" {
│
╵
╷
│ Error: Error creating instance: googleapi: Error 400: Invalid value for field 'resource.name': 'vm_instance_1-name'. Must be a match of regex '(?:[a-z](?:[-a-z0-9]{0,61}[a-z0-9])?)', invalid
│
│   with google_compute_instance.vm_instance_1,
│   on gcp-instance.tf line 9, in resource "google_compute_instance" "vm_instance_1":
│    9: resource "google_compute_instance" "vm_instance_1" {
│
╵

[yunkon-kim]

This PR will be merged as is. Separate troubleshooting will be performed. (see #34)