[DT][NFC] Trim unnecessary IRs for materialize_encoding_x86_64.mlir test. (iree-org#22332)

The revision drops hal ops and iree_tensor_ext ops as many as possible;
improves legacy checks.

To make review eaiser, it leaves the SSA names of core ops and checks
unchanged.

It is a step towards iree-org#20825

Signed-off-by: hanhanW <[email protected]>
Signed-off-by: Philipp <[email protected]>

Author: hanhanW