[flang][MLIR][OpenMP] Emit `UpdateDataOp` from `!$omp target update` (#75345)

Emits MLIR op corresponding to `!$omp target update` directive. So far,
only motion types: `to` and `from` are supported. Motion modifiers:
`present`, `mapper`, and `iterator` are not supported yet.

This is a follow up to #75047 & #75159, only the last commit is relevant
to this PR.