[Core] Add correctness tests for SpaceToDepth and MobileClip Attention fusion (#28168)
### Description
Add correctness tests for fusions introduced in
https://github.com/microsoft/onnxruntime/pull/27883 and
https://github.com/microsoft/onnxruntime/pull/27747. The tests
introduced in those PRs only check if fusion went through but not if the
fused nodes produced semantically right results as the unfused
subgraphs. Adding those tests to prevent accidental breakage in case
something changed in the fused node's backing kernel implementation.
### Motivation and Context
Adress test coverage gap