Features/discovery return counts by ds

[noctillion]

Here the discovery endpoint was extended to support per-dataset entity counts, improving granularity for multi-dataset environments. It introduces helpers for fetching and censoring by-dataset counts, and adds them to the response

[codecov]

Codecov Report

❌ Patch coverage is 93.18182% with 3 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.75%. Comparing base (9b24cc2) to head (6673cb2).

Files with missing lines	Patch %	Lines
chord_metadata_service/discovery/censorship.py	85.00%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #606      +/-   ##
===========================================
- Coverage    93.76%   93.75%   -0.01%     
===========================================
  Files          130      130              
  Lines         5083     5124      +41     
  Branches       480      489       +9     
===========================================
+ Hits          4766     4804      +38     
- Misses         221      222       +1     
- Partials        96       98       +2     

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[davidlougheed]

this code doesn't currently handle the case where users do not have dataset level counts permissions... we need to consider perhaps returning a nested structure with projects and datasets.