revert discardable transformation (#10905)

* Revert "Properly wrap discarded statements (#10322)"

This reverts commit 15584879b9.

* add test for implicit discard after defer
* enable t10241 again
* make C++ tests green again

tests/discard/tdiscardable.nim

@@ -3,6 +3,8 @@ output: '''
 tdiscardable
 1
 1
+something defered
+something defered
 '''
 """
 
@@ -45,3 +47,21 @@ proc foo: (proc: int) =
   return bar
 
 discard foo()
+
+# bug #10842
+
+proc myDiscardable(): int {.discardable.} =
+  discard
+
+proc main1() =
+  defer:
+    echo "something defered"
+  discard myDiscardable()
+
+proc main2() =
+  defer:
+    echo "something defered"
+  myDiscardable()
+
+main1()
+main2()