This change adds support for documenting interfaces and their methods. A tablegen generator for the interface documentation is also added(gen-op-interface-doc).
Documentation is added to an OpInterface via the `description` field:
def MyOpInterface : OpInterface<"MyOpInterface"> {
let description = [{
My interface is very interesting.
}];
}
Documentation is added to an InterfaceMethod via a new `description` field that comes right before the optional body:
InterfaceMethod<"void", "foo", (ins), [{
This is the foo method.
}]>,
PiperOrigin-RevId: 270965485