Show mismatching values when DeepCompile test fails (#7618)
This PR improves error message when DeepCompile test fails.
Tests of DeepCompile occasionally fail
([example](https://github.com/deepspeedai/DeepSpeed/actions/runs/18160078309/job/51688736712?pr=7604))
because of mismatching loss values.
To make sure this is not a synchronization bug that causes `nan` loss
values, the change in this PR shows the mismatching values. We can
consider increasing the tolerances once we confirm the mismatch is
reasonable.
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Signed-off-by: Masahiro Tanaka <mtanaka@anyscale.com>
