core: Ensure EvalReadDataApply is called on expanded destroy nodes

During accpeptance tests of some of the first data sources (see
hashicorp/terraform#6881 and hashicorp/terraform#6911),
"unknown resource type" errors have been coming up. Traced it down to
the ResourceCountTransformer, which transforms destroy nodes to a
graphNodeExpandedResourceDestroy node. This node's EvalTree() was still
indiscriminately using EvalApply for all resource types, versus
EvalReadDataApply. This accounts for both cases via EvalIf.

terraform/transform_resource.go

@@ -894,7 +894,23 @@ func (n *graphNodeExpandedResourceDestroy) EvalTree() EvalNode {
 				&EvalRequireState{
 					State: &state,
 				},
-				&EvalApply{
+				// Make sure we handle data sources properly.
+				&EvalIf{
+					If: func(ctx EvalContext) (bool, error) {
+						if n.Resource.Mode == config.DataResourceMode {
+							return true, nil
+						}
+
+						return false, nil
+					},
+
+					Then: &EvalReadDataApply{
+						Info:     info,
+						Diff:     &diffApply,
+						Provider: &provider,
+						Output:   &state,
+					},
+					Else: &EvalApply{
 						Info:     info,
 						State:    &state,
 						Diff:     &diffApply,
@@ -902,6 +918,7 @@ func (n *graphNodeExpandedResourceDestroy) EvalTree() EvalNode {
 						Output:   &state,
 						Error:    &err,
 					},
+				},
 				&EvalWriteState{
 					Name:         n.stateId(),
 					ResourceType: n.Resource.Type,