[JVM+IR] Migrate/improve receiver mangling test suite

compiler/testData/codegen/asmLike/receiverMangling/innerClass.kt

@@ -1,3 +0,0 @@
-class Foo {
-    inner class Bar
-}

compiler/testData/codegen/asmLike/receiverMangling/innerClass.txt

@@ -1,9 +0,0 @@
-public final class Foo$Bar : java/lang/Object {
-    final Foo this$0
-
-    public void <init>(Foo this$0)
-}
-
-public final class Foo : java/lang/Object {
-    public void <init>()
-}

compiler/testData/codegen/asmLike/receiverMangling/simple.kt

@@ -1 +0,0 @@
-fun String.foo(a: Int) {}

compiler/testData/codegen/asmLike/receiverMangling/simple.txt

@@ -1,3 +0,0 @@
-public final class SimpleKt : java/lang/Object {
-    public final static void foo(java.lang.String $this$foo, int a)
-}