Add support to de-emphasize debuggers in run list

[WardenGnaw]

This PR supports hiding debuggers in VS Code similar to the when clause, but when will disable the debugger from being used, but the new field hiddenWhen will allow the debugger to still be used. If hiddenWhen is evaluated to be true, it will hide the debuggers in the list.

Example usage in package.json to hide the debugger selection if the C# Dev Kit is installed.

    "type": "coreclr",
    "hiddenWhen ": "dotnet.debug.serviceBrokerAvailable",
    "label": ".NET 5+ and .NET Core",

Before:

After:

Fixes: #184457

[gjsjohnmurray]

I find the name hard to understand. Did you consider alternatives such as hiddenWhen?

[WardenGnaw]

I find the name hard to understand. Did you consider alternatives such as hiddenWhen?

I agree hiddenWhen captures the intent of this. I'll switch it to that.