Port the make_callback test addon from #219 and enable node-api/test_async in node-tests

[kraenhansen]

Two test-coverage follow-ups deferred from #398. Both validate functionality that Hermes' first-party Node-API implementation provides on its own (independent of the hermes_napi_host integration), so they were split out as test-infrastructure work.

1. Port the make_callback test addon from #219

napi_async_init / napi_async_destroy / napi_make_callback are provided natively by the vendored Hermes since the static_h adoption (the injector binds the full symbol surface), which obsoletes #219's host-side C++ implementation — but its test addon (tests/make_callback/: addon.c adapted from Node's own test plus a promise-less driver asserting receiver/argument/return-value plumbing) ports directly to the packages/node-addon-examples/tests/<name>/ pattern established there and in #398:

• Copy addon.c, addon.js, binding.gyp from Implementation of napi_async_init, napi_async_destroy, napi_make_callback #219 (credit @paradowstack), add the checked-in CMakeLists.txt per the tests/async template and a package.json with a unique name (e.g. make-callback-test).
• Register under suites.tests in packages/node-addon-examples/src/index.ts.

Expected to pass as-is against next — a failure would be a real conformance finding against Hermes' implementation.

2. Enable node-api/test_async in packages/node-tests

The entry exists but is commented out in scripts/copy-tests.mts's ALLOW_LIST. Two independent blockers:

• common shims: the bundling pipeline aliases ../../common to packages/node-tests/common.ts, which currently only exports buildType. Upstream test.js uses common.mustCall. A faithful mustCall/mustCallAtLeast/mustNotCall needs a home for its verification step: upstream checks call counts at process exit, which has no analogue in the long-lived mocha-remote app — the shim needs a per-test verification hook wired into the generated suite (e.g. an afterEach-style flush exposed from common.ts).
• <uv.h> in the C side: upstream test_async.c includes <uv.h> directly, so enabling it also needs a small uv shim along the lines of the pthread-based one written for tests/threadsafe-function/addon.c in Implement hermes_napi_host for async work and thread-safe functions #398 (or an upstream contribution making the test buildable without libuv).

Note on value: the behavioral coverage largely overlaps the hand-written tests/async addon (create/queue/cancel/delete, cancel-while-queued via pool saturation — upstream's MAX_CANCEL_THREADS 6 trick is the same one tests/async already uses — plus the #398 additions for thread identity and cancel-while-running). The win from enabling the upstream suite is conformance tracking against Node itself rather than new coverage, which is also why it wasn't a blocker for #398.