CLI: Fix -it not being able to pipe stdout (apple#951)

Fixes apple#949

Typically if one fd is a tty, it's common for all 3 of stdio to be the
same, but that is not always the case. In our case we were using our
Terminal type from Containerization to comb through err/out/in and give
us a type backed by one of the 3 if -t was supplied. It happens that
stderr is the first we check, so our Terminal() is backed by fd 2. This
change modifies things so that we always initialize our Terminal if
asked for with fd 0, and out/err are backed by their corresponding
correct fd number.

## Type of Change
- [x] Bug fix
- [ ] New feature  
- [ ] Breaking change
- [ ] Documentation update

## Testing
- [x] Tested locally
- [ ] Added/updated tests
- [ ] Added/updated docs

Author: dcantah

Sources/ContainerClient/ProcessIO.swift

@@ -48,7 +48,7 @@ public struct ProcessIO: Sendable {
             if !tty || !interactive {
                 return nil
             }
-            let current = try Terminal.current
+            let current = try Terminal(descriptor: STDIN_FILENO)
             try current.setraw()
             return current
         }()
@@ -94,13 +94,9 @@ public struct ProcessIO: Sendable {
         let (stream, cc) = AsyncStream<Void>.makeStream()
         if let stdout {
             configuredStreams += 1
-            let pout: FileHandle = {
-                if let current {
-                    return current.handle
-                }
-                return .standardOutput
-            }()
 
+            stdio[1] = stdout.fileHandleForWriting
+            let pout = FileHandle.standardOutput
             let rout = stdout.fileHandleForReading
             rout.readabilityHandler = { handle in
                 let data = handle.availableData
@@ -111,7 +107,6 @@ public struct ProcessIO: Sendable {
                 }
                 try! pout.write(contentsOf: data)
             }
-            stdio[1] = stdout.fileHandleForWriting
         }
 
         let stderr: Pipe? = {