[DevOps]: Make `machine_name` a required argument with no default in ingestion core config

### Task Details

`machine_name` should be a required argument with no default. Right now it defaults to `perlmutter`, which doesn't make sense when running the ingestion scripts on machines beyond NERSC/perlmutter.

Refer to https://github.com/E3SM-Project/simboard/pull/169#issuecomment-5185827937

### Steps to Complete

_No response_

### Additional Notes

_No response_

Start by locating the ingestion core configuration and the current machine_name default, then review the referenced pull request discussion for context. The change is done when machine_name must be supplied explicitly and ingestion scripts no longer assume perlmutter; verify the affected configuration or script entry points with a non-perlmutter machine name.

Written by the indexing model from the issue text.