vscode cppdbg should not launch a new terminal when using attach mode

Related: https://github.com/microsoft/vscode-cpptools/issues/14118

Environment

• OS and version: Windows 10
• VS Code: 1.107.1
• C/C++ extension: 1.29.3
• OS and version of remote machine (if applicable): RHEL 8
• GDB / LLDB version: 16.3

Bug Summary and Steps to Reproduce

Bug Summary:
When using attach mode, vscode cppdbg should not start a new terminal. The terminal is always empty and useless.

Steps to reproduce:

1. Install C/C++ extension and Tasks Shell Input extension.

2. launch.json:

   {
       "version": "0.2.0",
       "configurations": [
           {
               "name": "(gdb) Attach",
               "type": "cppdbg",
               "request": "attach",
               "program": "${workspaceFolder}/main",
               "processId": "${input:processID}",
               "MIMode": "gdb"
           }
       ],
       "inputs": [
           {
               "id": "processID",
               "type": "command",
               "command": "shellCommand.execute",
               "args": {
                   "command": "cat ${workspaceFolder}/main.pid",
                   "useFirstResult": true
               }
           }
       ]
   }
   

3. main.c:

   #include <stdio.h>
   #include <stdlib.h>
   #include <unistd.h>
   
   int main() {
       FILE *fp = fopen("main.pid", "w");
       if (!fp) {
           return EXIT_FAILURE;
       }
       fprintf(fp, "%ld\n", (long) getpid());
       fclose(fp);
   
       while (1) {
           puts("Hello");
           sleep(3);
       }
       return EXIT_SUCCESS;
   }
   

4. Compile and run:

   gcc -g main.c -o main
   

   ./main
   

5. Run - Start Debugging

We need the "attach" mode because the actual program need a special way to launch.

But in "attach" mode, the terminal "cppdbg: main" is useless (and distracting). It will always be empty, because the program prints and reads at its own terminal.

Maybe cppdbg should not launch a terminal when using attach mode, or we need an option at launch.json to make cppdbg not to launch a terminal.

Reproduce the issue from launch.json using the cppdbg attach configuration, main.c, and GDB 16.3, then start debugging through VS Code. Trace the attach-mode path responsible for creating the terminal and determine whether completion means suppressing it by default or adding a launch.json option; verify that the terminal is no longer opened for attach sessions.