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/constructor-basic.js

@@ -0,0 +1,17 @@
+load("test-common.js");
+
+try {
+  function Foo() {
+      this.x = 123;
+  }
+
+  assert(Foo.prototype.constructor === Foo);
+
+  var foo = new Foo();
+  assert(foo.constructor === Foo);
+  assert(foo.x === 123);
+
+  console.log("PASS");
+} catch (e) {
+  console.log("FAIL: " + e);
+}