Mesh in restore checkpoint when target is None

Hello,
I've been looking into how to migrate to Orbax checkpoints. In the [guide](https://flax.readthedocs.io/en/latest/guides/orbax_upgrade_guide.html), you expose the parameter `mesh` in `restore_args_from_target`, but then I went and look into the [documentation](https://github.com/google/flax/blob/25ab83c34e07c0be652301d200a8b7ab703f0cb3/flax/training/orbax_utils.py#L41) and found that the `mesh` parameter is deprecated, and it should be specified within `target`.

All good in the case `target` is available. However, in my use case `target` may be not available, but I may want to restore a checkpoint from a certain mesh anyway. Do you have any suggestion on how to workaround this problem?

Related to this, here a second question for me to better understand how this works 😄 Shouldn't there be the possibility to pass a `mesh` parameter also when saving a checkpoint?