ds4_test: make metal-tensor-equivalence test deterministic on CUDA/ROCm

[alantsev]

make metal-tensor-equivalence test deterministic to avoid flaky test runs

Keep ./ds4_test --metal-tensor-equivalence execution deterministic

$ ./ds4_test --metal-tensor-equivalence

metal-tensor-equivalence:
ds4: CUDA backend initialized on AMD Radeon 8060S Graphics (sm_115)
ds4: CUDA registered 80.76 GiB model mapping for device access
ds4: CUDA preparing model tensor mappings: 80.24 GiB
ds4: CUDA q8 fp16 cache limit reached; using q8 kernels (request=64.00 MiB cached=7.94 GiB limit=8.00 GiB)
ds4: CUDA startup model preparation covered 80.76 GiB of tensor spans in 0.314s
ds4: cuda backend initialized for graph diagnostics
ds4-test: Tensor equivalence candidate route=auto
ds4: CUDA backend initialized on AMD Radeon 8060S Graphics (sm_115)
ds4: CUDA registered 80.76 GiB model mapping for device access
ds4: CUDA preparing model tensor mappings: 80.24 GiB
ds4: CUDA q8 fp16 cache limit reached; using q8 kernels (request=64.00 MiB cached=7.94 GiB limit=8.00 GiB)
ds4: CUDA startup model preparation covered 80.76 GiB of tensor spans in 0.346s
ds4: cuda backend initialized for graph diagnostics
ds4-test: Tensor equivalence short_italian_fact top1 ref=108149 cand=108149 top5_overlap=5/5 overlap=20/20 max_rank_delta=0 rms=0 max_abs=0 top20_max_abs=0
ds4-test: Tensor equivalence short_italian_fact largest deltas: id=0 ref=-15.0155 cand=-15.0155 abs=0 id=1 ref=19.9358 cand=19.9358 abs=0 id=2 ref=-55.9084 cand=-55.9084 abs=0 id=3 ref=17.8982 cand=17.8982 abs=0 id=4 ref=26.0747 cand=26.0747 abs=0
ds4-test: Tensor equivalence short_code_completion top1 ref=9854 cand=9854 top5_overlap=5/5 overlap=20/20 max_rank_delta=0 rms=0 max_abs=0 top20_max_abs=0
ds4-test: Tensor equivalence short_code_completion largest deltas: id=0 ref=-2.66161 cand=-2.66161 abs=0 id=1 ref=21.3162 cand=21.3162 abs=0 id=2 ref=-45.7824 cand=-45.7824 abs=0 id=3 ref=10.9651 cand=10.9651 abs=0 id=4 ref=25.8229 cand=25.8229 abs=0
ds4-test: Tensor equivalence short_reasoning_plain top1 ref=926 cand=926 top5_overlap=5/5 overlap=20/20 max_rank_delta=0 rms=0 max_abs=0 top20_max_abs=0
ds4-test: Tensor equivalence short_reasoning_plain largest deltas: id=0 ref=-3.03494 cand=-3.03494 abs=0 id=1 ref=23.3849 cand=23.3849 abs=0 id=2 ref=-42.7991 cand=-42.7991 abs=0 id=3 ref=16.0927 cand=16.0927 abs=0 id=4 ref=18.5051 cand=18.5051 abs=0
ds4-test: Tensor equivalence long_memory_archive top1 ref=32111 cand=32111 top5_overlap=5/5 overlap=20/20 max_rank_delta=0 rms=0 max_abs=0 top20_max_abs=0
ds4-test: Tensor equivalence long_memory_archive largest deltas: id=0 ref=-8.42831 cand=-8.42831 abs=0 id=1 ref=19.284 cand=19.284 abs=0 id=2 ref=-50.653 cand=-50.653 abs=0 id=3 ref=10.6968 cand=10.6968 abs=0 id=4 ref=21.0302 cand=21.0302 abs=0
ds4-test: Tensor equivalence long_code_audit top1 ref=671 cand=671 top5_overlap=5/5 overlap=20/20 max_rank_delta=0 rms=0 max_abs=0 top20_max_abs=0
ds4-test: Tensor equivalence long_code_audit largest deltas: id=0 ref=-4.50487 cand=-4.50487 abs=0 id=1 ref=19.7669 cand=19.7669 abs=0 id=2 ref=-47.0626 cand=-47.0626 abs=0 id=3 ref=16.7405 cand=16.7405 abs=0 id=4 ref=23.0197 cand=23.0197 abs=0
ds4-test: Tensor summary route=auto cases=5 capture_fail=0 logits_fail=0 greedy_fail=0 top1_mismatch=0 min_top5_overlap=5/5 min_overlap=20/20 worst_rank_delta=0 worst_rms=0 worst_max_abs=0 worst_top20_max_abs=0
metal-tensor-equivalence: OK
ds4 tests: ok

With this change I got 100% reproducible test (I use ROCm version).

without this change I am getting ~6% failures for this test on a long context due to enabled non-deterministic atomics.
If the current behaviour is expected - i.e. we test non-determinism on CUDA/ROCm - we could increase the thresholds instead.