[FIR2IR] Don't replace while loop and when branch body blocks with single expression. Skip some empty blocks.

https://youtrack.jetbrains.com/issue/KT-60264/K2-while-loop-body-block-sometimes-replaced-with-single-expression

Merge-request: KT-MR-12035
Merged-by: Vladimir Sukharev <Vladimir.Sukharev@jetbrains.com>

compiler/testData/ir/irText/expressions/sam/samConversionsWithSmartCasts.fir.kt.txt

@@ -1,30 +1,40 @@
 fun test1(a: Function0<Unit>) {
   when {
-    a is Runnable -> runStatic(r = a /*as Runnable */)
+    a is Runnable -> { // BLOCK
+      runStatic(r = a /*as Runnable */)
+    }
   }
 }
 
 fun test2(a: Function0<Unit>) {
   when {
-    a is Runnable -> J().run1(r = a /*as Runnable */)
+    a is Runnable -> { // BLOCK
+      J().run1(r = a /*as Runnable */)
+    }
   }
 }
 
 fun test3(a: Function0<Unit>) {
   when {
-    a is Runnable -> J().run2(r1 = a /*as Runnable */, r2 = a /*as Runnable */)
+    a is Runnable -> { // BLOCK
+      J().run2(r1 = a /*as Runnable */, r2 = a /*as Runnable */)
+    }
   }
 }
 
 fun test4(a: Function0<Unit>, b: Function0<Unit>) {
   when {
-    a is Runnable -> J().run2(r1 = a /*as Runnable */, r2 = b /*-> @FlexibleNullability Runnable? */)
+    a is Runnable -> { // BLOCK
+      J().run2(r1 = a /*as Runnable */, r2 = b /*-> @FlexibleNullability Runnable? */)
+    }
   }
 }
 
 fun test5(a: Any) {
   when {
-    a is Runnable -> J().run1(r = a /*as Runnable */)
+    a is Runnable -> { // BLOCK
+      J().run1(r = a /*as Runnable */)
+    }
   }
 }
 
@@ -54,3 +64,4 @@ fun test8(a: Function0<Unit>) {
 fun test9() {
   J().run1(r = ::test9 /*-> @FlexibleNullability Runnable? */)
 }
+