Review recent changes to V8 public API

[pinepain]

It mostly mean to review https://github.com/v8/v8/commits/master/include/v8.h commits and figure our which one are relevant and what we have to implement and create issues for each specific feature or group of features.

[pinepain]

At the moment we lack of modules and dynamic import support which recently went stable and also some minor APIs. Created tasks to implement relevant v8 changes in php-v8.