This PR bumps Vitest from v2 to v4. As far as I know we don't use any
Vitest specific features in our tests, but had to upgrade the
`vitest.workspace.ts` file to a `vitest.config.ts` file instead.
The only features we use are the typical `describe`, `it`, `test`, and
`expect` functions.
The only other part we use is `vi.spyOn` and `vi.fn` but those didn't
change in API either.
The test shards were removed to prevent errors. Not all suites have
enough files / tests to be broken up into 3 parts so Vitest now errors
when that happens.
### Test plan
1. All tests should pass in CI.
2. All integration tests should pass in CI.
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Co-authored-by: Jordan Pittman <jordan@cryptica.me>
479b725cd3