src: clean up WHATWG URL parser, round 2

This batch has some pretty heavy-duty changes, so reviewing commit-by-commit is probably preferred.

• Reduce indentation

  For some reason the linter never caught it, but in all other source files namespaces do not affect indentation. Link to whitespace-free diff

• Refactor node_url.h and node_url.cc

  A lot of inlined functions and lookup tables never needed to be in the header. Now that the header is going to be used more frequently in other areas of the codebase, it is best these things go into the actual implementation file.

• Prefer templates over macros

  Many character checks were implemented as macros. Implement them as templatized inline functions for better type checking.

• Do not export ARG_* flags in url binding

  They are not used by the JS layer.

Checklist

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

Affected core subsystem(s)

src, url