Closes https://github.com/microsoft/playwright/issues/23964.
Trace snapshots are a best-effort snapshots of the browser DOM, but we
can't guarantee them to be exactly what the browser showed. One example
of this is `canvas` elements, where you just can't see their contents.
That makes snapshots useful, but not perfect.
For those cases where the snapshot doesn't show everything, this PR
introduces a new setting to show a screenshot instead. You won't be able
to scroll or inspect the DOM or select a locator anymore. But if the
snapshot was missing something, or displaying something wrong, you can
now check the screenshot instead.
When two attachments have the same content sha1, we used the first one's
name for the downloaded file, no matter which one the user clicked to
download. Now we pass the name explicitly.
References #31912.