Ephemeral write only attributes (#3171)

Signed-off-by: Andrei Ciobanu <andrei.ciobanu@opentofu.org>
Signed-off-by: Christian Mesh <christianmesh1@gmail.com>

internal/command/e2etest/testdata/ephemeral-workflow/mod/main.tf

@@ -1,10 +1,12 @@
 variable "in" {
-  type = string
+  type        = string
   description = "Variable that is marked as ephemeral and doesn't matter what value is given in, ephemeral or not, the value evaluated for this variable will be marked as ephemeral"
-  ephemeral = true
+  ephemeral   = true
 }
 
 output "out1" {
-  value = var.in
-  ephemeral = true // NOTE: because
+  value     = var.in
+  // NOTE: because this output gets its value from referencing an ephemeral variable,
+  // it needs to be configured as ephemeral too.
+  ephemeral = true
 }