Previously, we forced a new worker for a new set of worker fixtures.
Now, we can reuse the worker by tearing down mismatching worker
fixtures between tests.
The new behavior allows all tests from a single file run in-order,
even when mixing various test types with different worker fixtures.
This is less efficient, but more predictable for the user.
Switching between worker fixtures is reported under "Reset Fixtures"
step inside "Before Hooks" and has a separate timeout.
We still force a new worker for each project and repeatEach index.
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