## Problem
I spent a few minutes seeing how fast I could get our regression test
suite to run on my workstation, for when I want to run a "did I break
anything?" smoke test before pushing to CI.
- Test runtime was dominated by a couple of tests that run for longer
than all the others take together
- Test concurrency was limited to <16 by the ports-per-worker setting
There's no "right answer" for how long a test should
be, but as a rule of thumb, no one test should run
for much longer than the time it takes to run all the
other tests together.
## Summary of changes
- Make the ports per worker setting dynamic depending on worker count
- Modify the longest running tests to run for a shorter time
(`test_duplicate_layers` which uses a pgbench runtime) or fewer
iterations (`test_restarts_frequent_checkpoints`).
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