Add workflow than can load ESS NeXus files

[SimonHeybrock]

This will be based on https://scipp.github.io/essreduce/generated/modules/ess.reduce.nexus.generic_workflow.GenericNeXusWorkflow.html#ess.reduce.nexus.generic_workflow.GenericNeXusWorkflow but some fixes in ScippNexus are required.

[SimonHeybrock]

Several problems in the NMX files from CODA prevent progress.

• https://jira.ess.eu/projects/ECDC/issues/ECDC-4297
• https://jira.ess.eu/projects/ECDC/issues/ECDC-4332
• Some missing depend_on='.' attributes.