debug: support compounds launch configurations

[vince-fugnitto]

Feature Description:

The goal is to support compound for debug launch configurations. Currently the compound launch configurations are not present in the dropdown, or supported in the launch.json schema:

Steps to Reproduce

1. start the application using theia as a workspace

2. open the debug view and select the dropdown

3. notice that both compound launch configurations are missing

   theia/.vscode/launch.json

   Lines 196 to 216 in f6c0689

   	"compounds": [
   	{
   	"name": "Launch Electron Backend & Frontend",
   	"configurations": [
   	"Launch Electron Backend",
   	"Attach to Plugin Host",
   	"Attach to Electron Frontend"
   	],
   	"stopAll": true
   	},
   	{
   	"name": "Launch Browser Backend & Frontend",
   	"configurations": [
   	"Launch Browser Backend",
   	"Attach to Plugin Host",
   	"Launch Browser Frontend"
   	],
   	"stopAll": true
   	}
   	]
   	}

4. notice that there is no context assistance for the compounds in the .vscode/launch.json file

[martin-fleck-at]

@vince-fugnitto Do you know if anyone is already working on this? If not I might have a look at it one of these days.

[vince-fugnitto]

@martin-fleck-at I'm not aware of anyone looking into so please go ahead :)