Prefer module fields for RSC server layer (#51179)
Follow up for #50548
There're some packages like `aws-sdk-js-v3` which doesn't have a exports field yet:
```
"main": "./dist-cjs/index.js",
"types": "./dist-types/index.d.ts",
"module": "./dist-es/index.js",
```
This PR let u pick up by the js assets based on main fields, will prefer `"module"` field instead of `"main"`
Closes NEXT-1286
