New Resource: `azurerm_data_protection_backup_policy_postgresql_flexi…

…ble_server` (#26024)

* New Resource: azurerm_data_protection_backup_policy_postgresql_flexible_server

* update code

* update resource

* update the resource

* refine resource

* use valut id

* use commonschema for vault it

* define data_store_type in the schema

* remove data_store_type for AzureBackupRule

* update format

* update code per comment

* add empty check

* update to int64