Allow inline workspace

[sheremet-va]

Clear and concise description of the problem

It would be nice to support inline workspace configuration:

export default defineConfig({
  test: {
    workspace: [
      {
        test: { 
          name: 'node', 
          environment: 'node'
        }, 
      },
      {
        test: { 
          name: 'jsdom', 
          environment: 'jsdom'
        }, 
      }
    ]
  }
})

This feature is required for https://github.com/vitest-dev/vitest/issues/6912 to make the migration easier.

Suggested solution

Alllow inlined workspace in the main config.

Alternative

No response

Additional context

Some questions:

1. Should inline workspace override the workspace file? Or should they be merged instead?
2. Is there a way to reduce the nesting?

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.