Add ir interpreter tests

compiler/testData/ir/interpreter/overrideExtension.kt

@@ -0,0 +1,14 @@
+@CompileTimeCalculation
+open class A {
+    open fun String.getSize() = this.length
+
+    fun returnSizeOf(str: String) = str.getSize()
+}
+
+@CompileTimeCalculation
+class B : A() {
+    override fun String.getSize() = -1
+}
+
+const val a = A().<!EVALUATED: `4`!>returnSizeOf("1234")<!>
+const val b = B().<!EVALUATED: `-1`!>returnSizeOf("1234")<!>