Feature request: support cross-providers resource move

[ms-henglu]

Terraform supports moved block which allows moving between two resources of different types. By supporting the new protocol, the resources from azurerm provider could be moved to azapi provider.

Here's an example:

resource "azurerm_resource_group" "test" {
  name     = "acctesthenglu1031"
  location = "East US"
}

# resource "azurerm_data_factory" "test" {
#   name                   = "heng"
#   location               = azurerm_resource_group.test.location
#   resource_group_name    = azurerm_resource_group.test.name
#   public_network_enabled = true
#   identity {
#     type = "SystemAssigned"
#   }
# }

moved {
  from = azurerm_data_factory.test
  to   = azapi_resource.factory
}

resource "azapi_resource" "factory" {
  type      = "Microsoft.DataFactory/factories@2018-06-01"
  parent_id = azurerm_resource_group.test.id
  name      = "heng"
  location  = "eastus"
  identity {
    type         = "SystemAssigned"
    identity_ids = []
  }

  body = {
    properties = {
      globalParameters    = {}
      publicNetworkAccess = "Enabled"
    }
  }
}

[stemaMSFT]

@ms-henglu does the end result behavior differ much from a removed and import block? Curious to see how this behaviors works across layers of modules as well.

[ms-henglu]

@stemaMSFT - Yes, there're some differences:

1. The major difference is the moved block could be used inside a module(it could also work across layers of modules), so for the module users, the migration could be transparent and without breaking changes.
2. The plan output is different:
   1. The removed + import output: One resource will be imported and one resource will be no longer managed by Terraform.
   2. The moved output: The azurerm resource has been moved to azapi resource.

[ms-henglu]

Completed via #668