[mlir] NFC: use !transform.any_op in relevant tests

Update various tests using Transform dialect extensions to pervasively
use `!transform.any_op` instead of `!pdl.operation`. Tests are sometimes
used as source of knowledge for best practices and these were doing the
opposite of what is considered best practices per
https://discourse.llvm.org/t/rfc-type-system-for-the-transform-dialect/65702.

Reviewed By: nicolasvasilache

Differential Revision: https://reviews.llvm.org/D150785