feat: better config __dirname support

[sapphi-red]

Description

This PR changes the way to implement __dirname/__filename/import.meta.url support in config files.

Before this PR, those values were replaced. But now it is injected at each files.
This will avoid some strange errors.

I tested this with the files below.

// vite.config.js
import './dep'

console.log('__dirname', __dirname)
console.log('__filename', __filename)
console.log('import.meta.url', import.meta.url)

;(() => {
  const __dirname = 'd'
  const __filename = 'f'
  console.log(__dirname, __filename)
})()

export default {}

// dep.js
console.log('[dep] __dirname', __dirname)
console.log('[dep] __filename', __filename)
console.log('[dep] import.meta.url', import.meta.url)

refs: #7846 (comment)

Additional context

---

What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

Before submitting the PR, please make sure you do the following

• Read the Contributing Guidelines.
• Read the Pull Request Guidelines and follow the Commit Convention.
• Check that there isn't already a PR that solves the problem the same way to avoid creating a duplicate.
• Provide a description in this PR that addresses what the PR is solving, or reference the issue that it solves (e.g. fixes #123).
• Ideally, include relevant tests that fail without this PR but pass with it.

[sapphi-red]

In CJS, the following code fails, so it is not a special thing.

const __dirname = ''

But here it also happens with ESM. This is the reason I left this note.

Also I didn't mention import.meta.url because __vite_injected_original_import_meta_url will rarely conflict.