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/JSON.stringify-proxy.js

@@ -1,18 +0,0 @@
-load("test-common.js");
-
-try {
-    let p = new Proxy([], {
-        get(_, key) {
-            if (key === "length")
-                return 3;
-            return Number(key);
-        },
-    });
-
-    assert(JSON.stringify(p) === "[0,1,2]");
-    assert(JSON.stringify([[new Proxy(p, {})]]) === "[[[0,1,2]]]");
-
-    console.log("PASS");
-} catch (e) {
-    console.log("FAIL: " + e);
-}