Put pieces in place for fiddle to support opfs, but more cleanup is required in the sqlite3.js/fiddle connection. bigIntEnabled now defaults to whether the Emscripten's module has bigint enabled. Add wasm-sensible defaults for several SQLITE_ENABLE/OMIT flags in sqlite3-wasm.c.

FossilOrigin-Name: 7c7fb7535e86b3960eea7f29ab7e6d5197c166b4ee64ad4a9bc0749f2869badc

ext/wasm/fiddle/fiddle.js

@@ -326,7 +326,7 @@
         }
     }
 
-    SF.worker = new Worker('fiddle-worker.js');
+    SF.worker = new Worker('fiddle-worker.js'+self.location.search);
     SF.worker.onmessage = (ev)=>SF.runMsgHandlers(ev.data);
     SF.addMsgHandler(['stdout', 'stderr'], (ev)=>SF.echo(ev.data));