Add docs/example for (de)serialization of framework types, especially collections

### Module version

```
v1.10.0 currently referenced by the docs
```

### Use-cases

I'm implementing an attribute with a complex type (list of nested objects). The docs [1][2] show how to define the schema, but only have cursory examples for converting to/from framework types to my own (backend) type hierarchy. I found some forum discussion and other provider code (see below) to implement the conversion myself, but an example in the framework docs itself really is missing in my opinion.

[1] https://developer.hashicorp.com/terraform/plugin/framework/handling-data/attributes/list-nested
[2] https://developer.hashicorp.com/terraform/plugin/framework/handling-data/attributes/object

### Attempted Solutions

Helpful links I found:
-
-
- #962

some other providers doing similar conversions:

-
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-

### Proposal

### References

Related:
- #258