Merge branch 'amiranda/59-add-adm_job_t-to-adm_adhoc_contex_t' into 'main'

Resolve "API does not provide facilities to communicate job and adhoc hostnames"

This MR extends the current API by introducing two new structures
`ADM_job_resources_t` and `ADM_adhoc_resources_t`.

- [x] `ADM_adhoc_resources_t` is renamed from `ADM_storage_resources_t` 
and now contains a list of nodes assigned for the adhoc storage instance 
(the PFS is more of a static thing, so it doesn't make sense to have a 
generic interface for this). An `ADM_adhoc_resources_t` argument is added 
to `ADM_adhoc_context_create()` and is propagated through RPCs. This 
allows resource managers (i.e. Slurm or the IC) to inform us about the 
nodes assigned for an `adhoc_storage`.
- [x] A new structure `ADM_job_resources_t` is added to the API, which for 
now contains a list of nodes assigned to a job. An `ADM_job_resources_t` 
argumet is added to `ADM_register_job()` and related functions and is 
propagated to `scord` via RPCs. This allows resource managers to inform 
`scord` about the nodes assigned for a job.

Closes #59

See merge request !43