[IR] Rewrite how interpreter works with the Unit result

This way interpreter works in more correct way. Every expression
produces some result, and if we don't need it, the interpreter will
discard it.

compiler/testData/ir/interpreter/object.kt

@@ -1,9 +1,7 @@
 @CompileTimeCalculation
 class A {
-    const val a = <!EVALUATED: `10`!>{ 10 }()<!> // lambda is needed to avoid computions by old frontend
-
     companion object {
-        const val static = <!EVALUATED: `-10`!>{ -10 }()<!>
+        const val static = <!EVALUATED: `-10`!>{ -10 }()<!> // lambda is needed to avoid computions by old frontend
 
         fun getStaticNumber(): Int {
             return Int.MAX_VALUE
@@ -21,7 +19,6 @@ object ObjectWithConst {
     fun concat(first: String, second: Any) = "$first$second"
 }
 
-const val num = <!EVALUATED: `10`!>A().a<!>
 const val numStatic = <!EVALUATED: `-10`!>A.static<!>
 const val numStaticFromFun = <!EVALUATED: `2147483647`!>A.getStaticNumber()<!>
 const val valFromObject = <!EVALUATED: `Value in a: 100`!>ObjectWithConst.b<!>