Add auto generated code for GL_EXT_tessellation_shader 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>