doc: multiple improvements in Stream docs

Add missing links, remove duplicate ones, fix constants and functions styling.
Minor lexical corrections.

PR-URL: nodejs#5009
Reviewed-By: Stephen Belanger <[email protected]>
Reviewed-By: Sakthipriyan Vairamani <[email protected]>
Reviewed-By: James M Snell <[email protected]>

Author: estliberitas