WIP Single engine in tests

[GianlucaFicarelli]

Local execution:

make destroy
time make test-local

- commit 178098e5 (main):
1081 passed, 29 warnings in 266.58s (0:04:26) 
user=137.55s system=8.08s cpu=50% total=4:46.69

- commit bf31c6b4 (PR)
1081 passed, 29 warnings in 168.89s (0:02:48)
user=133.22s system=6.28s cpu=74% total=3:07.74

CI execution:

- commit 178098e5 (main):
1081 passed, 29 warnings in 532.17s (0:08:52)
https://github.com/openbraininstitute/entitycore/actions/runs/30009134111/job/89212447652

- commit 84bfe2c7 (PR)
1081 passed, 29 warnings in 403.45s (0:06:43)
https://github.com/openbraininstitute/entitycore/actions/runs/30110409413/job/89538236571

[codecov]

Codecov Report

❌ Patch coverage is 96.55172% with 1 line in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
app/db/session.py	94.73%	0 Missing and 1 partial ⚠️

Flag	Coverage Δ
pytest	97.78% <96.55%> (-0.08%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
app/application.py	96.15% <100.00%> (+0.07%)	⬆️
app/db/model.py	99.14% <ø> (ø)
app/queries/common.py	98.24% <100.00%> (+0.01%)	⬆️
app/db/session.py	69.09% <94.73%> (-7.23%)	⬇️

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