tests: fix sql_alchemy_db fixture for timescale

[joseph-sentry]

there's a deadlock error that happens where the timescale background worker is running background jobs and we're altering the schema of the tables on which it's running the background job on, so we stop the background worker momentarily to allow the migrations to run.

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Codecov Report

All modified and coverable lines are covered by tests ✅

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Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.72%. Comparing base (dba53c5) to head (71420fd).
Report is 3 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1177   +/-   ##
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  Coverage   97.72%   97.72%           
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  Files         453      453           
  Lines       37117    37125    +8     
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+ Hits        36273    36281    +8     
  Misses        844      844           

Flag	Coverage Δ
integration	42.80% <100.00%> (+0.01%)	⬆️
unit	90.55% <100.00%> (+<0.01%)	⬆️

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[Swatinem]

so this is the source of flakyness in CI?

[joseph-sentry]

so this is the source of flakyness in CI?

imo this is the source of flakiness.

i'm not sure why we haven't run into this on prod yet, probably because the background worker on prod doesn't run jobs as often, but i don't see why that same deadlock failure wouldn't be possible to run into on prod