perf: omit unnecessary work from ElectronRenderFrameObserver::ShouldNotifyClient()
- (perf) GetBlinkPreferences() returns a const&, so we can use that
reference instead of making a temporary copy
- (perf) Don't create url object unless it's needed.
- (refactor) Move is_main_world() and is_isolated_world() from the
header into an anonymous namespace in the .cc file so they can
be inlined and made constexpr
* fix(extensions): set lowest isolated world id
* refactor: move world IDs into separate header file
Several files are including electron_render_frame_observer.h just for the world IDs.
