SignalR ts client transport has unexpected behaviour about transport when calling withUrl() twice

### Is there an existing issue for this?

- [X] I have searched the existing issues

### Describe the bug

In my project I basically do this:
```
const hubConnectionBuilder = new signalR.HubConnectionBuilder();
const connectionBuilder = hubConnectionBuilder
.withUrl("http://example.com/1", {transport: HttpTransportType.LongPolling})
.build();
```

and at a later point I just want to change the URL so I call:
`connectionBuilder.withUrl("http://example.com/2")`

For me unexpectedly this changes the transport back to original and tries websockets for http://example.com/2 but websockets are blocked so it fails.

I proposed this PR to change this behaviour:
https://github.com/dotnet/aspnetcore/pull/51875

I am new here so I don't expect this pullrequest to be flawless or maybe it won't even get accepted because the behaviour is as designed.

PS: Can you give me a tip how to run the SignalR/ts/signalr tests I'd appreciate it. Wrote the test but didn't know how to execute it except by creating a Pullrequest... Also not sure if my log line really works because it is nullable until build()

### Expected Behavior

calling withUrl() second time without the optional parameter will not overwrite transport from LongPolling with undefined

### Steps To Reproduce

https://github.com/dotnet/aspnetcore/pull/51875

### Exceptions (if any)

_No response_

### .NET Version

"@microsoft/signalr": "^7.0.5",

### Anything else?

In debug logging I receive this unexpected logging:
Debug: Selecting transport 'WebSockets'.
-> altough I've selected LongPolling on first withUrl() call and didn't specify it in second withUrl call