fix: Real support for .Net xUint test

[Yumitoya8569]

Current progress

The current version (1.1.3) does not work when running C# xUnit tests at all.
The reason is that the test process is not attached to the debugger.
This PR uses a workaround to attach it.

Follow-up

Currently, it uses a presumed name (testhost) to scan processes and obtain the PID.
There should be a better approach in the future.

[Yumitoya8569]

@microsoft-github-policy-service agree

[Yumitoya8569]

Update

1. Fixed an issue where the server would fail to start if the .csproj and .cs files were not in the same directory.
2. Fixed an issue where continuous requests from the agent would cause the server to crash.

Follow-up

Continuous requests cause the server to crash due to the transport implementation.
Additionally, the singleton stateless mode described in the StreamableHTTPServerTransport doc does not actually work.
So for now, just fixed it with a workaround.
There should be a better approach in the future.