[#172976853] Enable autoscaling in appgateway and apigateway

[uolter]

Due to this issue: hashicorp/terraform-provider-azurerm#6188
You need to run terrafrom with a custom azure provider.

And this should be the change in the plan:

resource "azurerm_application_gateway" "application_gateway" {
        enable_http2        = false
        id                  = "/subscriptions/****************/resourceGroups/io-p-rg-external/providers/Microsoft.Network/applicationGateways/io-p-ag-apigateway"
        location            = "westeurope"
        name                = "io-p-ag-apigateway"
        resource_group_name = "io-p-rg-external"
        tags                = {}
        zones               = []

      + autoscale_configuration {
          + max_capacity = 10
          + min_capacity = 2
        }