Add support for browser mode tracesDir config to Vitest CLI

Clear and concise description of the problem

As part of the Vitest Trace views, there is a tracesDir config setting:
https://vitest.dev/guide/browser/trace-view.html

Right now there doesn't seem to be a way to configure it via the CLI. You can set --browser.trace, but not something like --browser.tracesDir.

Would you all be willing to add support for that?

Configuring the traces output via the CLI is helpful in situations where you need a specific output path that can't be statically defined in a config file. The CLI also already supports output paths for other directories (--coverage.reportsDirectory, --attachmentsDir, etc.), so one for tracesDir would match with those options.

Suggested solution

Add a new --browser.tracesDir setting to the Vitest CLI. This setting should work the same as the existing one for the config file.

Validations

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

Start with Vitest's CLI handling for the existing --browser.trace option and compare it with the browser tracesDir setting described in the trace-view and CLI documentation. Trace how CLI values map to browser configuration, then add the matching option and verify that it produces the same output-path behavior as the config-file setting.