Unexpected behavior for @nn.compact_name_scope

```py
import jax
from flax import linen as nn
from jax import random
import jax.numpy as jnp

class Foo(nn.Module):
@nn.compact_name_scope
def up(self, x):
return self._embed(x) + nn.Dense(4)(x)

def _embed(self, x):
return nn.Dense(4)(x)

Foo().init(random.PRNGKey(0), jnp.zeros((3, 4)), method=Foo.up)
```

This throws error: `flax.errors.AssignSubModuleError: Submodule Dense must be defined in `setup()` or in a method wrapped in `@compact` (https://flax.readthedocs.io/en/latest/api_reference/flax.errors.html#flax.errors.AssignSubModuleError)`

However when I replace `@nn.compact_name_scope` with `@nn.compact` it does work.

So it seems methods wrapped in `@nn.compact_name_scope` can only call other methods that are wrapped in that as well, which is different behavior than `@nn.compact`.

Is this behavior intended? If so, it should probably be documented. Otherwise would it be possible to fix it?