Add implicit cast from `IEnumerable<T>` to `ConditionedList<T>`

[premun]

Example that should compile:

new Job("Foo")
{
    Pool = new HostedPool()
    {
        Demands = new[] { "ImageOverride -equals 1es-ubuntu-2004" }
    },
}

but it requires new() as is new ConditionedList<string> which might be unclear.