Run continuation asynchronously in context of events

[nvborisenko]

This PR make Playwright events waiter more friendly with sync-over-async pattern.

Issue

This piece of code demonstrates deadlock. Real code, you can run it (I ran it in NUnit).

await page.RunAndWaitForResponseAsync(async () =>
{
    await page.GotoAsync("https://linked.in");
}, new Regex(".*google.*"));

//await Task.Yield();

Task.Run(async () => await page.Locator(".nav__logo-link").ClickAsync()).GetAwaiter().GetResult();

Here GetAwaiter().GetResult() is blocked. We understand that it is anti-pattern, sync-over-async. To fix it we can add await Task.Yield(). But what if Playwright can be more friendly for dummy users like me?

Solution?

This PR allows tasks continuations asynchronously. Now the code above just works.