[bartlomieju]

Fixes #32968

V8 14.7+ ships a native queueMicrotask on the global object behind the
--enable-queue-microtask flag. This PR enables the flag and routes
queueMicrotask through the native builtin instead of the custom
op_queue_microtask op.

• op_queue_microtask (a nofast op that just called
  isolate.enqueue_microtask) is removed. Our queueMicrotask wrapper
  enqueues through V8's native builtin — no op-boundary crossing per call.
• Error handling is unchanged: the wrapper still runs the callback under a
  try/catch and routes uncaught exceptions through reportExceptionCallback
  (the error event / uncaughtException), so ordering and async context
  (AsyncLocalStorage) are preserved.
• V8 skips experimental globals while snapshotting, so the native function is
  only installed at runtime. Internal extensions capture queueMicrotask from
  the primordials at snapshot time, so the wrapper is a stable reference for
  them that lazily grabs the native builtin on first use.

Performance

Release build, Apple M-series, best-case (min) per run vs. the current
canary (op-based, same V8 14.9.207.2-rusty):

Benchmark	Baseline (op_queue_microtask)	This PR
enqueue + drain ×1000	~24 µs	~12 µs
per-call enqueue cost	~17 ns	~5.7 ns

Net: ~2× faster on a full enqueue+drain roundtrip, ~3× lower per-call
enqueue cost.

// enqueue + drain roundtrip
Deno.bench("queueMicrotask x1000", async () => {
  await new Promise((resolve) => {
    let n = 1000;
    for (let i = 0; i < 1000; i++) queueMicrotask(() => { if (--n === 0) resolve(); });
  });
});