make ref path available in `write_dispatched` and `read_dispatched` callback

[flying-sheep]

Please describe your wishes and possible alternatives to achieve the desired result.

As pointed out in #2436, just having store.name and elem_name isn’t enough, see e.g.

You can put anything in uns, so is /uns/thing/obsm a dict in a dict in .uns or an AxisArrays mapping in a nested AnnData in .uns?

So it would make sense to give context by passing the correct anndata.acc path available