[feat] custom graceful stop timeout

### Description

# feat

custom graceful stop timeout

## background

I found:

Currently, graceful stop will wait for 3m, then enforce stop.

Try to figure out how to custom graceful stop timeout.

But seems no way, due to hard code.

https://github.com/lima-vm/lima/blob/master/pkg/driver/qemu/qemu_driver.go#L446-L448

```go
func (l *LimaQemuDriver) Stop(ctx context.Context) error {
return l.shutdownQEMU(ctx, 3*time.Minute, l.qCmd, l.qWaitCh)
}
```

## actual

graceful stop timeout is hard code as 3m

# expected

custom graceful stop timeout

Start in pkg/driver/qemu/qemu_driver.go at LimaQemuDriver.Stop and trace how shutdownQEMU receives the current three-minute timeout. Identify the existing configuration path and tests around stopping, then make the graceful-stop timeout configurable and verify that the selected duration is used before enforcement.

Written by the indexing model from the issue text.