Extend TimeSeriesExecutor to num_chunks_per_job

Related to shards and zarr v3 #4260 , it would be cool for individual jobs to loop through multiple chunks.

The change can take place only in the TimeSeriesExecutor and global job kwargs

If did a proof of concpet here : #4833
I think I prefer: num_chunk_per_batch for the variable.
The current is absolutly not tested. Just to demonstrated how easy it can be done and usefull for zarr v3 shards