OpenAIClient is not respecting HttpClient from DI

### Is there an existing issue for this?

- [x] I have searched the existing issues

### Describe the bug

The OpenAIClient that Aspire registers in DI doesn't respect other services registered in DI, in particular HttpClient. That means any configuration for HttpClient, such as resiliency pipelines from Microsoft.Extensions.Http.Resilience, an ILogger plugged into that HttpClient's logging, and so on, end up not being respected.

### Expected Behavior

If no options were provided in DI explicitly, the Aspire component should respect any HttpClient that was registered in DI. Here's what Semantic Kernel does, for example:
https://github.com/microsoft/semantic-kernel/blob/cd40e2e079f1a657b25334e004f3c2e36f24a59c/dotnet/src/Agents/OpenAI/OpenAIClientProvider.cs#L130-L140
turning off the built-in resiliency mechanisms of OpenAIClient and instead deferring to the HttpClient and the policies configured for it.
```C#
private static void ConfigureClientOptions(HttpClient? httpClient, ClientPipelineOptions options)
{
options.AddPolicy(CreateRequestHeaderPolicy(HttpHeaderConstant.Names.SemanticKernelVersion, HttpHeaderConstant.Values.GetAssemblyVersion(typeof(OpenAIAssistantAgent))), PipelinePosition.PerCall);

if (httpClient is not null)
{
options.Transport = new HttpClientPipelineTransport(httpClient);
options.RetryPolicy = new ClientRetryPolicy(maxRetries: 0); // Disable retry policy if and only if a custom HttpClient is provided.
options.NetworkTimeout = Timeout.InfiniteTimeSpan; // Disable default timeout
}
}
```

### Steps To Reproduce

_No response_

### Exceptions (if any)

_No response_

### .NET Version info

_No response_

### Anything else?

_No response_