List(Nested()) doesn't use `many` in the nested schema

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```python
from marshmallow import Schema, fields, post_dump

class ItemSchema(Schema):
id = fields.Integer()
name = fields.String()

@post_dump(pass_many=True)
def query_extra_data(self, data, many, **kwargs):
print(f'post_dump called: {many=} {data=}')

class TestSchema(Schema):
items = fields.List(fields.Nested(ItemSchema))

data = {'items': [
{'id': 1, 'name': 'foo'},
{'id': 2, 'name': 'bar'},
{'id': 3, 'name': 'snafu'},
]}

TestSchema().dump(data)
```

This gives me the following output:

```
post_dump called: many=False data={'name': 'foo', 'id': 1}
post_dump called: many=False data={'name': 'bar', 'id': 2}
post_dump called: many=False data={'name': 'snafu', 'id': 3}
```

However, I expected this:

```
post_dump called: many=True data=[{'name': 'foo', 'id': 1}, {'name': 'bar', 'id': 2}, {'name': 'snafu', 'id': 3}]
```

This is a problem when the `post_dump` hook queries stuff from a database as I would end up with n individual queries instead of a single one where I can use IN to efficiently get data for all the objects in the list.

Are there any decent workarounds for this? One thing that came to my mind is using this instead of `List(Nested)`, but it feels much uglier...

```python
items = fields.Function(lambda data: ItemSchema(many=True).dump(data['items']))
```

Start with the List(Nested(...)) serialization path and the @post_dump(pass_many=True) hook shown in the report. Reproduce the example with TestSchema().dump(data), then inspect how fields.List and fields.Nested propagate many; done means the nested hook receives one batched call without changing existing scalar behavior.

Written by the indexing model from the issue text.