[mlir] switch the transform loop extension to use types

[mlir] switch the transform loop extension to use types

Add types to the Loop (SCF) extension of the transform dialect.

See https://discourse.llvm.org/t/rfc-type-system-for-the-transform-dialect/65702

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D135587