MapHub extension with custom hub hame

### 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 set up local development using an Azure Signalr instance in a way where developer APIs that handle incoming SignalR requests don't interfere with each other. I had the same issue with Azure Web Pubsub and it was addressed there with this PR (in response to a feature request): https://github.com/Azure/azure-sdk-for-net/pull/47022

I tried using unique paths per machine when registering the hub (e.g. "/hub1", "/hub2"), but there was still interference.

### Describe the solution you'd like

Adding extension method for specifying custom hub name:

```
public void Configure(IApplicationBuilder app)
{
app.UseEndpoints(endpoint =>
{
endpoint.MapHub("/sampleHubPath", "customHubName");
});
}
```

### Additional context

_No response_

Start by reviewing the existing MapHub extension methods and the linked Azure Web PubSub pull request, then trace how the hub path and name are registered. Done means a custom hub name can be supplied alongside the path as shown, with the behavior covered by the relevant existing tests.

Written by the indexing model from the issue text.