Fix async sample synchronization patterns with timeouts

[Copilot]

Async samples used brittle Thread.sleep() or indefinite CountDownLatch.await(), causing unreliable behavior under slow networks or hanging indefinitely on failures.

Changes:

• Sample00_UpdateDefaultsAsync.java: Replaced Thread.sleep(10) with CountDownLatch + doFinally() callback, added 30s timeout
• Sample06_GetAnalyzerAsync.java: Added 10s timeout to existing CountDownLatch.await()

Both samples now use deterministic synchronization with timeout handling:

CountDownLatch latch = new CountDownLatch(1);

client.getDefaults()
    .doFinally(signalType -> latch.countDown())
    .subscribe(/* ... */);

if (!latch.await(30, TimeUnit.SECONDS)) {
    System.err.println("Operation timed out");
    System.exit(1);
}

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