Test: Improve automated issue management

[chrmarti]

Testing #32238

Complexity 2

• Any OS: @bpasero
• Any OS: @ramya-rao-a

In one of our satellite repos or a personal repo:

• Make sure the VSCode bot is installed (Repo Settings > Integrations & Services)
• Configure automatic assignment by checking in a file .github/assignment.yml with:

{
    perform: true,
    assignees: [ yourgithubid ]
}

• Verify new issues are automatically assigned to the listed (comma separated) GitHub accounts.
• Verify that if you assign a new issue to someone before submitting it, no automatic assignment is done.

In our main repo, configure multiple assignees (e.g., for workbench) in: https://github.com/Microsoft/vscode/blob/master/.github/classifier.yml

• Verify only one of these assignees is assigned for that label and it is randomly picked.

Assigning @bpasero because he specifically asked for the random assignment and the classifier is really only operational on our main repo at this time.

[bpasero]

I added @sandy081 and @isidorn with me to workbench, let's see how that turns out.

[ramya-rao-a]

I can confirm that the workbench labelled issues are now being assigned to either @bpasero @isidorn or @sandy081