os: refactor structure of the os module

Refactoring the structure of the os module to use the more efficient module.exports = {} pattern.

Also adds simple Symbol.toPrimitive support for each of the os methods that return simple primitives.

Lastly, removes extraneous console output from the test-os.js

Checklist

• make -j4 test (UNIX), or vcbuild test (Windows) passes
• tests and/or benchmarks are included
• commit message follows commit guidelines

Affected core subsystem(s)

os