skaffold apply - support manifests on stdin, similar to kubectl apply -f -

Please add support to `skaffold apply` for using Kubernetes manifests from stdin, similar to what `kubectl apply -f -` does.

Obviously it'd be nice to support the same `-f -` are that kubectl does but I can't due to that already being taken for `-f skaffold.yaml`, but could still support accepting k8s manifests from stdin if no file args are given.

The current workaround of outputting to a file and then supplying a file arg is ok, but accepting from stdin would be nice to have too as a more unix-like behaviour to support CLI pipes.

### Expected behavior

```
skaffold render |
skaffold apply
```

### Actual behavior

```
skaffold render |
skaffold apply
`apply` requires at least one manifest argument
write /dev/stdout: broken pipe
```

### Information

- Skaffold version: 1.27.0
- Operating system: Mac
- Installed via: Homebrew