[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/localFunctions/genericClass.ir.txt

@@ -0,0 +1,9 @@
+@kotlin.Metadata
+public final class<<T:Ljava/lang/Object;>Ljava/lang/Object;>  A {
+    // source: 'genericClass.kt'
+    public final <()TT;> method f(): java.lang.Object
+    public final <()TT;> method getResult(): java.lang.Object
+    public <(TT;)V> method <init>(p0: java.lang.Object): void
+    private final static <<T:Ljava/lang/Object;>(LA<TT;>;)TT;> method f$g(p0: A): java.lang.Object
+    private final field <TT;> result: java.lang.Object
+}