Copy all of the type classes from src/type into ast.
Required the merging of:
* type::Struct into the existing ast::Struct - ast::Struct now has a name.
* type::AccessControl into the existing ast::AccessControl enumerator - The old ast::AccessControl enumerator is now ast::AccessControl::Access
Bug: tint:724
Change-Id: Ibb950036ed551ec769c6d3d2c8fb411809cf6931
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48383
Kokoro: Kokoro <noreply+kokoro@google.com>
Reviewed-by: Antonio Maiorano <amaiorano@google.com>
Commit-Queue: Ben Clayton <bclayton@google.com>
Ben Clayton