[FIR JS] Add more tests for JS_NAME_CLASH and JS_FAKE_NAME_CLASH

^KT-59425 Related
^KT-59370 Related

js/js.translator/testData/box/inheritance/inheritExtensionsWithSameNames.kt

@@ -0,0 +1,17 @@
+open class Class {
+    fun String.test(): String = "O"
+    val String.test: String
+        get() = "K"
+}
+
+// This case is only relevant for the JS Legacy BE and is not applicable to the JS IR backend,
+// as the IR BE can resolve such name collisions.
+@Suppress("JS_FAKE_NAME_CLASH")
+class MyClass1 : Class()
+
+fun box(): String {
+    val s = ""
+    return with(MyClass1()) {
+        s.test() + s.test
+    }
+}