[lldb-dap] use workspaceFolder in vscode configurations. (llvm#164320)

`workspaceRoot` was deprecated in [september 2017
release](https://code.visualstudio.com/updates/v1_17#_workspacefolder-in-launchjson-and-tasksjson)

Author: da-viper

lldb/tools/lldb-dap/package.json

@@ -453,7 +453,7 @@
               "cwd": {
                 "type": "string",
                 "description": "Program working directory.",
-                "default": "${workspaceRoot}"
+                "default": "${workspaceFolder}"
               },
               "env": {
                 "anyOf": [
@@ -883,10 +883,10 @@
             "type": "lldb-dap",
             "request": "launch",
             "name": "Debug",
-            "program": "${workspaceRoot}/<your program>",
+            "program": "${workspaceFolder}/<your program>",
             "args": [],
             "env": [],
-            "cwd": "${workspaceRoot}"
+            "cwd": "${workspaceFolder}"
           }
         ],
         "configurationSnippets": [
@@ -897,10 +897,10 @@
               "type": "lldb-dap",
               "request": "launch",
               "name": "${2:Launch}",
-              "program": "^\"\\${workspaceRoot}/${1:<your program>}\"",
+              "program": "^\"\\${workspaceFolder}/${1:<your program>}\"",
               "args": [],
               "env": [],
-              "cwd": "^\"\\${workspaceRoot}\""
+              "cwd": "^\"\\${workspaceFolder}\""
             }
           },
           {