[cppvsdbg] Allow stdin to the debuggee

Type: Debugger

Describe the bug

• OS and Version: Windows 10 (1903)
• VS Code Version: 1.39.2
• C/C++ Extension Version: 0.26.1
• Other extensions you installed: CMake Tools (1.2.1)
• A clear and concise description of what the bug is.
  When launching the console debugger, COUT text is displayed correctly. CIN input is not passed to the program.

To Reproduce
launch.json:
launch.json.txt

main.cpp:
main.cpp.txt

Debug console output...
Loaded 'D:\Users\micro\Desktop\workspace\ITP365\itp365_20201_hw01\build\main.exe'. Symbols loaded.
Loaded 'C:\Windows\System32\ntdll.dll'. Cannot find or open the PDB file.
Loaded 'C:\Windows\System32\kernel32.dll'. Cannot find or open the PDB file.
Loaded 'C:\Windows\System32\KernelBase.dll'. Cannot find or open the PDB file.
Loaded 'C:\Windows\System32\msvcp140d.dll'. Cannot find or open the PDB file.
Loaded 'C:\Windows\System32\vcruntime140d.dll'. Cannot find or open the PDB file.
Loaded 'C:\Windows\System32\ucrtbased.dll'. Cannot find or open the PDB file.
The thread 11604 has exited with code 0 (0x0).
Please select...
1. Encrypt
2. Decrypt
?. Quit
1
2
The thread 32696 has exited with code 0 (0x0).
The thread 18488 has exited with code 0 (0x0).

The program '[4716] main.exe' has exited with code 0 (0x0).

Additional context
I'm teaching a C++ data structures class in January. I'd really like to use VSCode (instead of VS and XCode). But I need local debugging working.

Reproduce the issue with the attached launch.json and main.cpp on Windows 10, then inspect the cppvsdbg console input path. Confirm that input entered during a console debugging session reaches the debuggee's cin; done when the sample program receives and processes stdin instead of exiting without it.