specsuite: Initial test for top-level attribute handling

specsuite/tests/structure/attributes/expected.hcl

@@ -0,0 +1,3 @@
+a = "a value"
+b = "b value"
+c = "c value"

specsuite/tests/structure/attributes/expected.hcldec

@@ -0,0 +1,11 @@
+object {
+  attr "a" {
+    type = string
+  }
+  attr "b" {
+    type = string
+  }
+  attr "c" {
+    type = string
+  }
+}

specsuite/tests/structure/attributes/expected.t

@@ -0,0 +1,10 @@
+result_type = object({
+  a = string
+  b = string
+  c = string
+})
+result = {
+  a = "a value"
+  b = "b value"
+  c = "c value"
+}