Add soft delete to workspace storage account

Fixes #4385

Add soft delete configuration to Workspace storage accounts.

* Add `blob_properties` block with `delete_retention_policy` and `container_delete_retention_policy` settings to `azurerm_storage_account` resource in `templates/workspaces/base/terraform/storage.tf`.
* Add `file_properties` block with `delete_retention_policy` settings to `azurerm_storage_account` resource in `templates/workspaces/base/terraform/storage.tf`.

---

For more details, open the [Copilot Workspace session](https://copilot-workspace.githubnext.com/microsoft/AzureTRE/issues/4385?shareId=XXXX-XXXX-XXXX-XXXX).

templates/workspaces/base/terraform/storage.tf

@@ -31,6 +31,21 @@ resource "azurerm_storage_account" "stg" {
   infrastructure_encryption_enabled = true
 
   lifecycle { ignore_changes = [infrastructure_encryption_enabled, tags] }
+
+  blob_properties {
+    delete_retention_policy {
+      days = 7
+    }
+    container_delete_retention_policy {
+      days = 7
+    }
+  }
+
+  file_properties {
+    delete_retention_policy {
+      days = 7
+    }
+  }
 }
 
 # Using AzAPI as AzureRM uses shared account key for Azure files operations