[Test] Save IR bytecode dumps from BytecodeListingHandler to .ir.txt file instead of _ir.txt

This is needed to keep consistency with other dumps and to allow
  test helper plugin to recognize those dumps

compiler/testData/codegen/bytecodeListing/sam/genericSamInterface.ir.txt

@@ -0,0 +1,16 @@
+@kotlin.Metadata
+synthetic final class<null>  TKt$sam$Sam$0 {
+    // source: 't.kt'
+    <null> method <init>(p0: kotlin.jvm.functions.Function0): void
+    public synthetic final <null> method get(): java.lang.Object
+    enclosing class TKt
+    private synthetic final field <null> function: kotlin.jvm.functions.Function0
+    inner (anonymous) class TKt$sam$Sam$0
+}
+
+@kotlin.Metadata
+public final class<null>  TKt {
+    // source: 't.kt'
+    public final static <<T:Ljava/lang/Object;>(Lkotlin/jvm/functions/Function0<+TT;>;)TT;> method genericSam(@org.jetbrains.annotations.NotNull p0: kotlin.jvm.functions.Function0): java.lang.Object
+    inner (anonymous) class TKt$sam$Sam$0
+}