FR: Make it easier to setup a launch configuration with CMake Tools

### Feature Request

When CMake Tools is present and the user is creating a debug configuration in `launch.json`, make it easier to configure a CMake provided target:

```json5
// Resolved by CMake Tools:
"program": "${command:cmake.launchTargetPath}",
```
This could be inserted (semi-)automatically in the `launch.json` configuration (with or without user prompt). So if a user is creating a CMake based project, having this setup would be a nice QoL improvement, which isn't as obvious if the user is not familiar with the details. It will be great if the extension promotes this option.

Maybe this also:

```json5
"environment": [
{
// add the directory where our target was built to the PATHs
// it gets resolved by CMake Tools:
"name": "PATH",
"value": "${env:PATH}:${command:cmake.getLaunchTargetDirectory}"
},
```

Taken from:

https://github.com/microsoft/vscode-cmake-tools/blob/main/docs/debug-launch.md

```json5
{
"version": "0.2.0",
"configurations": [
{
"name": "(gdb) Launch",
"type": "cppdbg",
"request": "launch",
// Resolved by CMake Tools:
"program": "${command:cmake.launchTargetPath}",
"args": [],
"stopAtEntry": false,
"cwd": "${workspaceFolder}",
"environment": [
{
// add the directory where our target was built to the PATHs
// it gets resolved by CMake Tools:
"name": "PATH",
"value": "${env:PATH}:${command:cmake.getLaunchTargetDirectory}"
},
{
"name": "OTHER_VALUE",
"value": "Something something"
}
],
"externalConsole": true,
"MIMode": "gdb",
"setupCommands": [
{
"description": "Enable pretty-printing for gdb",
"text": "-enable-pretty-printing",
"ignoreFailures": true
}
]
}
]
}
```

Start with docs/debug-launch.md and the launch.json example referenced in the issue to understand the existing CMake Tools substitutions. Trace where launch configurations are created or assisted, then define completion as making the CMake target path available in a debug configuration, with the optional PATH setup handled consistently.

Written by the indexing model from the issue text.