Add support in basetypes for ListValues.ElementsValuePointer

### Module version

```
github.com/hashicorp/terraform-plugin-framework v1.16.1
```

### Use-cases

When I'm in an update function, I sometimes have to deal with `*[]string` for a particular attribute in an update request.
It would be helpful to have a way right from `types.List` to have something ready to be written inside the type.

### Attempted Solutions

I can have ad-hoc conversions inside the code of the update but it seems cumbersome to do it for all the different pointer on slice that have to be handled.

### Proposal

Add to the `types.List` a method to have a pointer on this list of element. A little bit similar to what exist for a string: `ValueStringPointer()`.

### References

- https://github.com/hashicorp/terraform-plugin-framework/blob/main/types/list_value.go
- https://github.com/hashicorp/terraform-plugin-framework/blob/main/types/basetypes/list_value.go