Add retryWithDelay() and retryUntil() methods to Queueable trait

[MagnusDot]

This PR adds two fluent methods to the Queueable trait to configure job retry behavior:

• retryWithDelay($delays) - Set custom backoff delays for job retries
• retryUntil($datetime) - Set the timestamp until which a job can be retried

These methods provide a cleaner, more fluent API for configuring retry behavior, consistent with other methods like delay(), onQueue(), and onConnection().

Changes

• Added $backoff and $retryUntil properties to the Queueable trait
• Added retryWithDelay($delays) method that accepts integers, arrays, DateTimeInterface, or DateInterval
• Added retryUntil($datetime) method that accepts DateTimeInterface or timestamp (int)
• Both methods return $this for method chaining
• Added comprehensive tests covering all supported parameter types and integration with the queue system

Usage

// Set custom retry delays
MyJob::dispatch()
    ->retryWithDelay([10, 30, 60, 120])
    ->retryUntil(now()->addHours(2));

// Or with a single delay
MyJob::dispatch()->retryWithDelay(60);

// Chain with other methods
MyJob::dispatch()
    ->retryWithDelay([10, 30, 60])
    ->retryUntil(now()->addDay())
    ->onQueue('high')
    ->onConnection('redis');## Testing

• All existing tests pass
• Added new tests covering

Backward Compatibility

This change is fully backward compatible. The existing behavior of setting $backoff and $retryUntil properties directly or via methods in job classes remains unchanged. These new methods simply provide a more convenient fluent API.

[rodrigopedra]

This is a breaking change for any jobs using the Queueable trait and already defining a typed $backoff or $retryUntil property.

class MyJob implements ShouldQueue 
{
    use Queueable;

    // this will break with the proposed change
    public int $backoff = 30;

    // ...
}

[taylorotwell]

We don't need another way to do this imo.