[mlir] add OperationType to the Transform dialect

Add a new OperationType handle type to the Transform dialect. This
transform type is parameterized by the name of the payload operation it
can point to. It is intended as a constraint on transformations that are
only applicable to a specific kind of payload operations. If a
transformation is applicable to a small set of operation classes, it can
be wrapped into a transform op by using a disjunctive constraint, such
as `Type<Or<[Transform_ConcreteOperation<"foo">.predicate,
Transform_ConcreteOperation<"bar">.predicate]>>` for its operand without
modifying this type. Broader sets of accepted operations should be
modeled as specific types.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D135586