LibJS: Reorganize tests into subfolders

Author: https://github.com/mattco98
Commit: 4c48c9d69d
Pull-request: https://github.com/SerenityOS/serenity/pull/2681
Reviewed-by: https://github.com/linusg

Libraries/LibJS/Tests/functions/function-this-in-arguments.js

@@ -0,0 +1,17 @@
+load("test-common.js");
+
+try {
+  assert(typeof this === "object");
+  assert(this === globalThis);
+
+  function Foo() {
+    this.x = 5;
+    assert(typeof this === "object");
+    assert(this.x === 5);
+  }
+
+  new Foo();
+  console.log("PASS");
+} catch (err) {
+  console.log("FAIL: " + err);
+}