src: do not use soon-to-be-deprecated V8 API

[targos]

V8 announced deprecation of the following methods:

• v8::Object::SetAccessor(...) in favor of v8::Object::SetNativeDataProperty(...),
• v8::ObjectTemplate::SetNativeDataProperty(...) with AccessControl parameter in favor of v8::ObjectTemplate::SetNativeDataProperty(...) without AccessControl parameter.

See https://crrev.com/c/5006387.

This slightly changes behavior of the following properties:

• process.debugPort (for worker processes),
• process.title (for worker processes),
• process.ppid.

The difference is that they will now behave like a regular writable JavaScript data properties - in case setter callback is not provided they will be be reconfigured from a native data property (the one that calls C++ callbacks upon get/set operations) to a real data property (so subsequent reads will no longer trigger C++ getter callbacks).