DataContent does not work with images or audio

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**Describe the bug**
Microsoft.Extensions.AI.DataContent message type is not supported with OnnxRuntimeGenAIChatClient client.

**To Reproduce**
Steps to reproduce the behavior:
```
using var onnxChatClient = new OnnxRuntimeGenAIChatClient(model);
byte[] imageBytes = File.ReadAllBytes(@"path.jpg");
var message = new(ChatRole.User, [
new TextContent(query),
new DataContent(imageBytes, "image/jpeg")
])
var response = onnxChatClient.GetResponseAsync([message]))
```
or
```
using var onnxChatClient = new OnnxRuntimeGenAIChatClient(model);
var message = new(ChatRole.User, [
new TextContent(query),
new UriContent(new Uri(@"https://path/to/image"), "image/jpeg")
]),
var response = onnxChatClient.GetResponseAsync([message]))
```
non-text content is not processed.
I'm expecting the model to "see" the attached image.

**Desktop (please complete the following information):**
- OS: [Win/Linux]
- Version [Microsoft.ML.OnnxRuntimeGenAI.Cuda 0.11.1]

Start by tracing how OnnxRuntimeGenAIChatClient handles the ChatRole.User content in the reproduction, comparing TextContent with DataContent and UriContent. Reproduce the issue with the provided image examples and confirm that non-text content is forwarded so the model can process the attachment.

Written by the indexing model from the issue text.