src: begin restructuring node.cc for better maintainability

Begins separating logical chunks of node.cc out into separate cc/h files for the purpose of making these easier to maintain and making node.cc less of a monolithic jumble of code.

There is quite a bit in node.cc that can be divided into logical chunks and this PR only handles two of those. Before going too much further with it tho, I'd like to make sure folks are on board with this.

The eventual goal is to refactor the bootstrap model for node.js with an eye towards improving start up times, supporting snapshots, and generally making the bootstrap more maintainable. However, because there is so much bundled into node.cc, it is difficult to refactor and reviewing changes to make sure nothing breaks is quite challenging.

And yes, the idea would be to backport these changes to LTS lines as well.

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• commit message follows commit guidelines