我已经在我的环境中复制了，并得到了预期的结果如下：
以下是我使用路由表创建Azure防火墙的代码，并遵循Document1和Document2：

provider "azurerm" {
  features {}
}

resource "azurerm_resource_group" "emo-rg" {
  name     = "emo-resources"
  location = "West Europe"
}

resource "azurerm_public_ip" "example" {
  name                = "testpip"
  location            = azurerm_resource_group.emo-rg.location
  resource_group_name = azurerm_resource_group.emo-rg.name
  allocation_method   = "Static"
  sku                 = "Standard"
}

resource "azurerm_virtual_network" "vnet" {
  name                = "ritwik-vnet"
  address_space       = ["10.0.0.0/16"]
  location            = azurerm_resource_group.emo-rg.location
  resource_group_name = azurerm_resource_group.emo-rg.name
}

resource "azurerm_subnet" "subnet" {
  name                 = "AzureFirewallSubnet"
  resource_group_name  = azurerm_resource_group.emo-rg.name
  virtual_network_name = azurerm_virtual_network.vnet.name
  address_prefixes     = ["10.0.1.0/24"]
}

resource "azurerm_firewall" "firewall" {
  name                = "testfirewall"
  location            = azurerm_resource_group.emo-rg.location
  resource_group_name = azurerm_resource_group.emo-rg.name
  sku_name            = "AZFW_VNet"
  sku_tier            = "Premium"

  ip_configuration {
    name                 = "configuration"
    subnet_id            = azurerm_subnet.subnet.id
    public_ip_address_id = azurerm_public_ip.example.id
  }
}

resource "azurerm_route_table" "westroute" {
  name                          = "West-route-table"
  location                      = azurerm_resource_group.emo-rg.location
  resource_group_name           = azurerm_resource_group.emo-rg.name
  disable_bgp_route_propagation = false

  route {
    name                 = "route1"
    address_prefix       = "0.0.0.0/0"
    next_hop_type        = "VirtualAppliance"
    next_hop_in_ip_address = azurerm_firewall.firewall.ip_configuration[0].private_ip_address
  }
}

输出：

执行terraform代码后创建的资源：

成功运行上述代码后，将使用以下IP地址创建路由表：

在Firewall中：