[mlir] Allows to query traits from types and attributes

Types and attributes now have a `hasTrait` function that allow users to check
if a type defines a trait.
Also, AbstractType and AbstractAttribute has now a `hasTraitFn` field to carry
the implementation of the `hasTrait` function of the concrete type or attribute.
This patch also adds the remaining functions to access type and attribute traits
in TableGen.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D105202