VSCode Extension: Add "Start if not running" command

I often make a dependent task for Azurite for my testing and launch tasks like so:

```
{
"label": "azurite",
"command": "${command:azurite.start}",
"problemMatcher": [],
"isBackground": true
},
```

However this always throws a bunch of toast errors if Azurite is already running. If I had a `azurite.startifnotrunning` command that would suppress error notifications about it already being started and only show errors if it failed would be very helpful. Thanks!