[Wasm] Move FirJsQualifierChecker to web.common and reuse in Wasm

#KT-56849

core/compiler.common.web/src/org/jetbrains/kotlin/js/JsHelpers.kt

@@ -0,0 +1,15 @@
+/*
+ * Copyright 2010-2023 JetBrains s.r.o. and Kotlin Programming Language contributors.
+ * Use of this source code is governed by the Apache 2.0 license that can be found in the license/LICENSE.txt file.
+ */
+
+package org.jetbrains.kotlin.js
+
+fun validateQualifier(qualifier: String): Boolean {
+    val parts = qualifier.split('.')
+    if (parts.isEmpty()) return false
+
+    return parts.all { part ->
+        part.isNotEmpty() && part[0].isJavaIdentifierStart() && part.drop(1).all(Char::isJavaIdentifierPart)
+    }
+}