PTY support

There is currently no built-in way in .NET to:

- Create a pseudo-terminal (PTY)
- Spawn a child process with the PTY as its controlling terminal
- Interact with the process via the PTY master side

We have recently introduced new APIs that will help:

- https://devblogs.microsoft.com/dotnet/process-api-improvements-in-dotnet-11/#processstartinfo.startdetached to run in a new session (setsid)
- https://devblogs.microsoft.com/dotnet/process-api-improvements-in-dotnet-11/#redirecting-standard-handles to redirect standard handles to PTY

We need to do some research, find the gaps, build a prototype and propose new APIs.