feat(worker): Drop annexed data after export

[nellh]

This initializes datasets with numcopies raised to 2 and drops local annexed content after every export. Adds an API endpoint to manually trigger a drop on existing datasets.

For many older datasets we have an s3-PRIVATE remote that was used for analysis jobs. This remote has not been active for years but we mark it dead before every drop to ensure inaccessible files in this remote are not counted by the numcopies setting.

[codecov]

Codecov Report

❌ Patch coverage is 63.63636% with 12 lines in your changes missing coverage. Please review.
✅ Project coverage is 42.95%. Comparing base (e89b3c7) to head (19a28ac).
⚠️ Report is 29 commits behind head on master.

Files with missing lines	Patch %	Lines
services/datalad/datalad_service/tasks/publish.py	58.33%	5 Missing ⚠️
services/datalad/datalad_service/handlers/drop.py	60.00%	4 Missing ⚠️
services/datalad/datalad_service/common/asyncio.py	57.14%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3599      +/-   ##
==========================================
+ Coverage   42.93%   42.95%   +0.01%     
==========================================
  Files         633      635       +2     
  Lines       33142    33173      +31     
  Branches     1479     1479              
==========================================
+ Hits        14231    14250      +19     
- Misses      18772    18784      +12     
  Partials      139      139              

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