Rename `all_chunk_coords` → `iter_chunk_coords` with deprecation shim for the old name

[maxrjones]

Opening an issue to track the deferred suggestion from #3802

imo the name all_chunk_coords doesn't convey that this is an iterator, but iter_chunk_coords would. if we need all_chunk_coords for backwards compat, can we deprecate that method and make it call iter_chunk_coords instead?

Originally posted by @d-v-b in #3802 (comment)