To support tessellation, code and auto generated code are added.
Entry points function, ShaderTypes, built in variables and constants,
builtin function barrier and patch keyword are added.

Bug: angleproject:3572
Change-Id: Ia5fe473e884466cb88cea7138e13377a1d7b4fa0
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2538393
Commit-Queue: Mohan Maiya <m.maiya@samsung.com>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Reviewed-by: Shahbaz Youssefi <syoussefi@chromium.org>