This patch:
- adds call logs to track screenshot timeouts, e.g. due to
waiting for web fonts
- makes sure all snapshot expectations have `.png` extension
- throws a polite error when given a buffer or a string instead of a
page or a locator
- removes stray NL between error description and call log
- makes sure `apiName` is always correct (and adds a test for it)
This option stops all kinds of CSS animations while doing screenshot:
- CSS animations
- CSS transitions
- Web Animations
Animations get different treatment depending on animation duration:
- finite animations are fast-forwarded to its end, issuing the
`transitionend` event.
- Infinite animations are resetted to its beginning, and then
resumed after the screenshot.
References #9938, fixes#11912
