Handle badly formed UUIDs as 404s for ContentNodeTree endpoint

[sentry-io]

ValueError: badly formed hexadecimal UUID string

Sentry Issue: KOLIBRI-BACKEND-2BK

ValueError: badly formed hexadecimal UUID string
(22 additional frame(s) were not displayed)
...
  File "uuid.py", line 177, in __init__
    raise ValueError('badly formed hexadecimal UUID string')

[rtibbles]

The events linked here also point to the fact that our facility_id filter for the FacilityDatasetViewset is badly implemented, and is not properly validating the facility_id value before putting it into a queryset.