Constructor argument checking rules are reorganized to make them
easier to understand and constructor node creation is made simpler.
This removes usage of constructor op codes from ParseContext. This
paves the way for getting rid of constructor op codes entirely, which
will remove duplicate information from the AST and simplify lots of
code.

This refactoring will make adding arrays of arrays slightly easier.

BUG=angleproject:1490
TEST=angle_unittests

Change-Id: I4053afec55111b629353b4ff7cb0451c1ae3511c
Reviewed-on: https://chromium-review.googlesource.com/498767
Commit-Queue: Olli Etuaho <oetuaho@nvidia.com>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>