doc: cleanups

- remove `node.js` dep., it has no effect as of #12747
- switch between LaTeX compilers, some cleanups
- CSS: fixup the print stylesheet, refactor highlighting code

Note: the only real highlighting change is for lifetimes which are now brown instead of red, the rest is just refactor of twos shades of red that look the same.
Also I made numbers highlighting for src in rustdoc a tint more clear so that it is less bothering.

@alexcrichton, @huonw