[release/v7.3.1] Fix Switch-Process to set termios appropriate for child process (#18572)

* add getting and setting termios

* chanage to use .NET exported function

* add comments

Co-authored-by: Steve Lee <slee@microsoft.com>

src/System.Management.Automation/engine/Modules/SwitchProcessCommand.cs

@@ -69,10 +69,12 @@ namespace Microsoft.PowerShell.Commands
             // need null terminator at end
             execArgs[execArgs.Length - 1] = null;
 
+            // setup termios for a child process as .NET modifies termios dynamically for use with ReadKey()
+            ConfigureTerminalForChildProcess(true);
             int exitCode = Exec(command.Source, execArgs);
-
             if (exitCode < 0)
             {
+                ConfigureTerminalForChildProcess(false);
                 ThrowTerminatingError(
                     new ErrorRecord(
                         new Exception(
@@ -108,6 +110,10 @@ namespace Microsoft.PowerShell.Commands
             CharSet = CharSet.Ansi,
             SetLastError = true)]
         private static extern int Exec(string path, string?[] args);
+
+        // leverage .NET runtime's native library which abstracts the need to handle different OS and architectures for termios api
+        [DllImport("libSystem.Native", EntryPoint = "SystemNative_ConfigureTerminalForChildProcess")]
+        private static extern void ConfigureTerminalForChildProcess([MarshalAs(UnmanagedType.Bool)] bool childUsesTerminal);
     }
 }