Add support for custom configuration for CosmosDB

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Is your feature request related to a problem? Please describe the problem.

I am trying to add Aspire to an existing project which requires composite indexes.

After several tentative, with custom commands, snapshot (via initial state) or trying directly to use the builder's required services, I just went with the code in base project way.
However in terms of design and separation of concerns, I'm not very happy with modifying the structure of my CosmosDB containers after their creation and at run time of my application.

### Describe the solution you'd like

I noticed a discussion here https://github.com/dotnet/aspire/discussions/8438 where it was suggested to add container options to pass along custom configuration. It seems like a good suggestion.

Another way could be to modify the API offering methods to add the values needed.
In my case for example it could look like:

```C#
var container = cosmosDbDatabase.AddContainer("container", "/partitionKey");
container.AddIndexingPolicy(new CompositePath() { Path = "/path/path", Order = CompositePathSortOrder.Descending });
```

### Additional context

_No response_