[js/web] ESM: use the bundled target as default export (#20991)
### Description
ESM: use the bundled target as default export
In this change, the default import of the following entries:
```
import from 'onnxruntime-web';
import from 'onnxruntime-web/all';
import from 'onnxruntime-web/webgpu';
```
will use the "bundled" version, which has no dynamic import.
This change should only apply to ESM on web.