ValueTask support

[mikasoukhov]

Here is some my own extensions (maybe will be interested to join with Nito's code, like you proj and use it):

public static async ValueTask AsValueTask<T>(this ValueTask<T> valueTask)
            => await valueTask;

        public static ValueTask<T> AsValueTask<T>(this Task<T> task)
            => new(task);

        public static ValueTask AsValueTask<T>(this Task task)
            => new(task);

        public static async ValueTask<T[]> WhenAll<T>(this IEnumerable<ValueTask<T>> tasks)
        {
            if (tasks is null)
                throw new ArgumentNullException(nameof(tasks));

            List<Exception> exceptions = null;

            var source = tasks.ToArray();

            var results = new T[source.Length];

            for (var i = 0; i < source.Length; i++)
            {
                try
                {
                    results[i] = await source[i].ConfigureAwait(false);
                }
                catch (Exception ex)
                {
                    exceptions ??= new List<Exception>(source.Length);
                    exceptions.Add(ex);
                }
            }

            if (exceptions is not null)
                throw new AggregateException(exceptions);

            return results;
        }

        public static async ValueTask WhenAll(this IEnumerable<ValueTask> tasks)
        {
            if (tasks is null)
                throw new ArgumentNullException(nameof(tasks));

            List<Exception> exceptions = null;

            var source = tasks.ToArray();

            for (var i = 0; i < source.Length; i++)
            {
                try
                {
                    await source[i].ConfigureAwait(false);
                }
                catch (Exception ex)
                {
                    exceptions ??= new List<Exception>(source.Length);
                    exceptions.Add(ex);
                }
            }

            if (exceptions is not null)
                throw new AggregateException(exceptions);
        }

        public static void Run(Func<ValueTask> getTask)
        {
            if (getTask is null)
                throw new ArgumentNullException(nameof(getTask));

            AsyncContext.Run(() => getTask().AsTask());
        }

        public static T Run<T>(Func<ValueTask<T>> getTask)
        {
            if (getTask is null)
                throw new ArgumentNullException(nameof(getTask));

            return AsyncContext.Run(() => getTask().AsTask());
        }

[BalassaMarton]

It would be quite inconvenient to have this name for a static utility class now that there's void ValueTask.