Add support for with `type: "text"` under a new experimental flag, following what webpack did (#89560)
## Summary
Adds support for the TC39 `import ... with { type: "text" }` proposal to Turbopack, allowing files to be imported as strings.
This is gated behind a new experimental flag `turbopackImportTypeText`.
```js
// next.config.js
export default {
experimental: {
turbopackImportTypeText: true,
},
}
```
```js
import text from './file.txt' with { type: 'text' }
// text is a string containing the file contents
```
### Related TC39 Proposals
- **[`type: "text"`](https://github.com/tc39/proposal-import-text)** - Stage 2 - Import file contents as a string
- **[`type: "bytes"`](https://github.com/nicolo-ribaudo/proposal-import-bytes)** - Stage 2.7 - Import file contents as a Uint8Array (already supported via `turbopackImportTypeBytes`)
### Implementation Details
- Created `TextSourceTransform` which transforms any file into an ES module exporting the file contents as a string
- Added `ResourceHasModifier` rule condition to match on ident modifiers, enabling proper module type resolution after source transforms
- Refactored `BytesSourceTransform` to use the same pattern for consistency
- Both transforms add a modifier to the ident (`text_module` / `bytes_module`) for uniqueness, allowing the same file to be imported both normally and with a type attribute
Using a source transform is simpler and allows the modules to participate in other bundler optimizations more easily (scope hoisting in particular)
This also fixes a few bugs where `with` imports would conflict with other module type rules:
* if you attempted to import a `.js` file with `type:'bytes'` didn't work since the file extension matching would trigger first.
* if you set a module type rule in your next config it would override the `with` attribute
## Test Plan
- Expanded e2e tests at `test/e2e/turbopack-import-with-type/`
next.js
b067991e - Add support for with `type: "text"` under a new experimental flag, following what webpack did (#89560)
