Deprecate workflow_target in ProcessSubscriptionTable and store_process_subscription()

[kvklink]

Closes #974

Workflow target is fetched from the workflow table, and the equivalent column in the ProcessSubscription table is now deprecated.

It is now deprecated to call store_process_subscription() with a target parameter.

[codspeed-hq]

CodSpeed Performance Report

Merging #986 will not alter performance

_{Comparing 974-deprecare-process-target (a43d40d) with main (e888879)}

Summary

✅ 12 untouched benchmarks

[codecov]

Codecov Report

Attention: Patch coverage is 70.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 84.36%. Comparing base (e888879) to head (a43d40d).

Files with missing lines	Patch %	Lines
orchestrator/workflows/steps.py	57.14%	2 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #986      +/-   ##
==========================================
- Coverage   84.39%   84.36%   -0.03%     
==========================================
  Files         213      213              
  Lines       10284    10287       +3     
  Branches     1010     1011       +1     
==========================================
  Hits         8679     8679              
- Misses       1337     1339       +2     
- Partials      268      269       +1     

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