Can't change a field in a copied embedded model that's part of a collection #228

# Bug

Given a model definition like this:

class E(EmbeddedModel):
f: int

class M(Model):
e: List[E]

model = M(e=[E(f=1)])
copy = instance.copy(deep=True)

When I call copy.e[0].f = 2
Then an `AttributeError: 'E' object has no attribute '__fields_modified__'` occurs

### Environment

- ODMantic version: 0.9.2
- MongoDB version: 5.0.9
- Pydantic infos (output of `python -c "import pydantic.utils; print(pydantic.utils.version_info())"`):

```
pydantic version: 1.9.1
pydantic compiled: True
install path: /lib/python3.10/site-packages/pydantic
python version: 3.10.4 (main, May 9 2022, 12:55:22) [GCC 9.3.0]
platform: Linux-5.4.0-73-generic-x86_64-with-glibc2.31
optional deps. installed: ['typing-extensions']
```

**Additional context**

This is a continuation of #228 .

Start by reproducing the shown deep-copy scenario with an EmbeddedModel collection, then inspect the copied embedded model when assigning to copy.e[0].f. Done means the assignment changes the copied field without raising AttributeError and the original model remains unaffected.

Written by the indexing model from the issue text.