[K/JS] Include jsFirEs6Test into jsFirCompilerTest tests

compiler/testData/codegen/boxWasmJsInterop/functionTypes.kt

@@ -1,5 +1,5 @@
 // Char issues
-// IGNORE_BACKEND: JS_IR
+// IGNORE_BACKEND: JS_IR, JS_IR_ES6
 
 // MODULE: main
 // FILE: externals.js

compiler/testData/codegen/boxWasmJsInterop/jsToKotlinAdapters.kt

@@ -1,4 +1,4 @@
-// IGNORE_BACKEND: JS_IR, JS
+// IGNORE_BACKEND: JS_IR, JS_IR_ES6, JS
 
 inline fun checkNPE(body: () -> Unit) {
     var throwed = false

compiler/testData/codegen/boxWasmJsInterop/nameClash.kt

@@ -1,4 +1,4 @@
-// IGNORE_BACKEND: JS_IR, JS
+// IGNORE_BACKEND: JS_IR, JS_IR_ES6, JS
 // FILE: file1.kt
 @JsFun("() => 42")
 private external fun clashName(): Int