Increase the throttle value of collecting mouse move and add a
transition time to the replayer's mouse. This may decrease the
size of mouse move data and make the replay movement more smooth.
Another change is to move and hover when click event is replayed.
This is to improve the replay of some programmatic click, such as
E2E tests.
In this commit we switched the sandbox strategy to use iframe's
sandbox attribute. Indeed we do not need delegate event anymore,
but need to add some styles into the iframe.
The details were documented in the sandbox part of internal design.
