This PR ensures that we pass Vite config file to the programmatic
`startTest` API from Vitest. It fixes the issue with plugins not loading
as well as other issues with the config file not being used.
This mainly affects a custom `configFile` option being passed to the
executor. The previous fix to additionally load in `plugins` via
overrides is causing plugins to load twice when the Vite config file is
picked up by Vitest (e.g. #27500).
## Current Behavior
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## Expected Behavior
<!-- This is the behavior we should expect with the changes in this PR
-->
## Related Issue(s)
<!-- Please link the issue being fixed so it gets closed when this is
merged. -->
Fixes#27500, #22001
402bae2ce1