[Console] Add ability to schedule alarm signals and a ConsoleAlarmEvent

[HypeMC]

Q	A
Branch?	7.2
Bug fix?	no
New feature?	yes
Deprecations?	no
Issues	Fix #47920
License	MIT

Part of #53508

This PR introduces the ability to schedule alarm signals and a console.alarm event. A command using this feature will automatically dispatch an alarm at the specified interval:

#[AsCommand('app:alarm')]
class AlarmCommand extends Command implements SignalableCommandInterface
{
    private bool $run = true;
    private int $count = 0;
    private OutputInterface $output;

    protected function initialize(InputInterface $input, OutputInterface $output): void
    {
        $this->getApplication()->setAlarmInterval(10);
    }

    protected function execute(InputInterface $input, OutputInterface $output): int
    {
        $this->output = $output;

        while ($this->run) {
            $this->count++;
            $output->writeln('execute '.$this->count);
            sleep(1);
        }

        $output->writeln('Done');

        return Command::SUCCESS;
    }

    public function getSubscribedSignals(): array
    {
        return [\SIGINT, \SIGALRM];
    }

    public function handleSignal(int $signal, false|int $previousExitCode = 0): int|false
    {
        if (\SIGINT === $signal) {
            $this->run = false;
            $this->output->writeln('Bye');
        } elseif (\SIGALRM === $signal) {
            $this->count = 0;
            $this->output->writeln('handleAlarm');
        }

        return false;
    }
}

The console.alarm event is dispatched on every SIGALRM signal:

#[AsEventListener(event: ConsoleAlarmEvent::class)]
final class ConsoleAlarmListener
{
    public function __invoke(ConsoleAlarmEvent $event): void
    {
        $event->getOutput()->writeln('ConsoleAlarmListener');
    }
}

[valtzu]

Btw, SIGALRM has the same effect as any other signal – it interrupts sleep & usleep. According to docs, one should check based on return code if the sleep was interrupted but I doubt many do that – and usleep returns void so for that it's impossible.

So if a command logic f.e. includes sleep(30); or $clock->sleep(30);, it will only sleep until next alarm, potentially causing unexpected behavior.

---

Another (old) thing I found that using SIGALRM to provide timer functionality may result in deadlock – not sure if it's still relevant (or if it ever was, for php).

[ro0NL]

cc @chalasr

we're running a userland implementation in prod, it works fine

[HypeMC]

getSignalRegistry throws a nearly identical exception, so it made sense to me to have it centralized.

[chalasr]

The implementation is now much simpler, looks good to me 👍

[fabpot]

Thank you @HypeMC.

[dkarlovi]

Thanks for working on this @HypeMC!