Add worker-style variant of the tests added in [ae24ac0f7dd9], but building this with wasmfs causes them to throw inexplicable exceptions from the Emscripten glue (without wasmfs it builds and runs fine, but storage is not persistent).

FossilOrigin-Name: 6401595e59179c5c0f6e51c5362cf4391787e7a55b9c6ca655746e30d3251f2b

ext/wasm/scratchpad-opfs-worker.js

@@ -0,0 +1,33 @@
+/*
+  2022-05-22
+
+  The author disclaims copyright to this source code.  In place of a
+  legal notice, here is a blessing:
+
+  *   May you do good and not evil.
+  *   May you find forgiveness for yourself and forgive others.
+  *   May you share freely, never taking more than you give.
+
+  ***********************************************************************
+
+  A basic test script for sqlite3-api.js. This file must be run in
+  main JS thread and sqlite3.js must have been loaded before it.
+*/
+'use strict';
+(function(){
+  const toss = function(...args){throw new Error(args.join(' '))};
+  const log = console.log.bind(console),
+        warn = console.warn.bind(console),
+        error = console.error.bind(console);
+
+  const W = new Worker("api/scratchpad-opfs-worker.js");
+  self.onmessage = function(ev){
+    ev = ev.data;
+    const d = ev.data;
+    switch(ev.type){
+        case 'stdout': log(d); break;
+        case 'stderr': error(d); break;
+        default: warn("Unhandled message type:",ev); break;
+    }
+  };
+})();