Better support for direct from JSONL

[ml-evs]

2024-09-27 11:52:31 - optimake - INFO - optimade.jsonl doesn't exist. Converting archive.

gets printed even if the JSONL path has been specified

[eimrek]

I think currently it works such that if you specify the jsonl directly with a different name than optimade.jsonl, it will tell you that message and then the conversion is just creating a symlink to optimade.jsonl.

But we could think how to improve this.