Read thread ID inside a test

[danilofuchs]

Clear and concise description of the problem

Our tests rely on a shared database connection, with --no-isolate and --no-threads as they may have side effects.

To speed it up, we want to run them in parallel, setting up multiple databases, one for each vitest thread.

Suggested solution

A field inside ctx.task that identifies the thread ID, so we can choose a different database.

Alternative

Run tests with --shard and use an environment variable for each shard.

Additional context

No response

Validations

• [X] Follow our Code of Conduct
• [X] Read the Contributing Guidelines.
• [X] Read the docs.
• [X] Check that there isn't already an issue that request the same feature to avoid creating a duplicate.

[sheremet-va]

There are already two variables:

https://vitest.dev/guide/migration.html#envs

1. VITEST_WORKER_ID is incremented for every new worker spawned
2. VITEST_POOL_ID is the number of worker (>= minWorkers && <=maxWorkers)