Add tasks to defaultobjectconverter

[tom-b-iodigital]

With this PR it's possible to call object methods that return tasks.

For example:

var engine = new Engine();
engine.SetValue("log", new Action<object>(Console.WriteLine))
    .SetValue("getTest", new Func<TestClass>(() => new()))
    .SetValue("__result", 0);

engine.Execute("""

(async () => {
    __result = "Before call";
    let testClass = getTest();

    __result = await testClass.GetDelayedStringAsync();
})();

""");

Console.WriteLine(engine.GetValue("__result"));


public class TestClass
{
    public async Task<string> GetDelayedStringAsync()
    {
        await Task.Delay(5000).ConfigureAwait(false);

        return "This is a delayed string";
    }
}

Before PR:

After PR:

[lahma]

Thanks for the PR, we also need tests to cover this new functionality - it's easy to break things later if behavior hasn't been tested.

[tom-b-iodigital]

I'll add some test cases

[tom-b-iodigital]

test cases added, let me know if you need anything else

[lahma]

LGTM, thank you for your contribution!

[uleelx]

This feature breaks the code before. In version 3.0.0, we can get the value synchronously: var result = sometask.result, and it seems much faster than Promise.then in v3.0.1 @tom-b-iodigital @lahma