Add Inline queue adapter that runs jobs on enqueue

[eldadfux]

What

Adds Adapter\Inline: a queue adapter that is also the publisher. enqueue() runs the matching job() in the same process and returns when the handler finishes. start() arms those handlers and returns — there is no consume loop and no worker process.

Use this when a single process should handle HTTP (or CLI) and its side-effects without a broker.

$adapter = new Inline();
$server = new Server($adapter);
$server->job('v1-mails')->action(function (Message $message) {
    // Runs inside enqueue(), before it returns
});
$server->start();

$adapter->enqueue(new Queue('v1-mails'), ['n' => 1]);

Behavior

• Failed handlers go through the Server error hook; enqueue() still returns true (same as a broker that accepted the message)
• Unknown queues (no registered job) are accepted and ignored
• getQueueSize() is always 0; retry() is a no-op
• Multi-queue Server::start() rejects a shared Consumer — Inline passes a callable factory so it can register many jobs
• Nested enqueue (job A enqueues job B) isolates DI context; concurrent Swoole requests keep that stack coroutine-local
• Uses processFrom() so process() does not read the uninitialized $this->queue property
• JSON-round-trips payloads before the handler runs (same as Redis/Nats), so handlers always see plain arrays — never live Document / stdClass objects. Empty objects become []. This keeps Appwrite workers adapter-agnostic.

Companion Appwrite change: appwrite/appwrite#13269 (_APP_QUEUE_ADAPTER=inline, no worker containers).

Test Plan

• vendor/bin/phpunit packages/queue/tests/Queue/Unit/InlineAdapterTest.php (11 tests) on PHP 8.3
• Full composer test is not run here: other queue unit files use PHP 8.5 syntax this host cannot parse