Change annotations parsing in bodies of operators

This change only matters in cases of if/when/for/while having braceless
blocks

Annotations on them are parsed now as on block-level expressions, i.e.
they're attached to the whole expression

compiler/testData/psi/annotation/at/blockLevelExpressions.kt

@@ -14,10 +14,35 @@ fun foo() {
     }
 
     for (i in 1..100)
-        // annotation is attached to `x4`
         @ann4
         x4 += foo4()
 
+    if (1 > 2)
+        @ann41
+        x41 += foo41()
+
+    if (3 > 4)
+        @ann42
+        x42 += foo42()
+    else
+        @ann43
+        x43 += foo43()
+
+    while (true)
+        @ann44
+        x44 += foo44()
+
+    do
+        @ann
+        x45 += foo45()
+    while (true)
+
+    when (1) {
+        1 ->
+            @ann46
+            x46 += foo46()
+    }
+
     a.filter {
         @ann5
         x5 += foo5()