Replace nested static_for lambdas with compile-time search helper

[tenpercent]

Summary

• Add sequence_find_value and find_in_tuple_of_sequences compile-time search helpers with O(1) template depth
• Replace nested static_for lambdas in TensorDescriptor::GetTransformAndItsUpperDimension and InitializeElementSize
• Apply same optimizations to TensorAdaptor

Supersedes #4287. Conflict-resolved rebase of ROCm/composable_kernel#3600 onto current develop.

Motivation

The TensorDescriptor and TensorAdaptor classes had excessive template instantiation from:

1. Nested static_for loops with lambdas creating unique closure types at every call site
2. generate_tuple with lambdas causing per-type instantiation overhead

The new helpers use constexpr array lookup and pack expansion instead of recursive template patterns, achieving O(1) template depth.

Results (example_grouped_conv_fwd_xdl_fp16, n=10, interleaved, -j1, -ftime-trace)

TU	Baseline (mean)	New (mean)	Delta	Wilcoxon p	Mann-Whitney p
grouped_conv_fwd_xdl_fp16 (host)	14,886 ms	13,353 ms	-10.3%	0.002	0.0002
grouped_conv_fwd_xdl_fp16 (device)	27,762 ms	25,629 ms	-7.7%	0.002	0.0002
Total (all TUs)	57,732 ms	54,030 ms	-6.4%

Unrelated TUs (device_memory, host_tensor, convolution_parameter) show no significant difference (p > 0.3), serving as negative controls.

Methodology

• 10 interleaved runs (baseline₁, new₁, baseline₂, new₂, ...) on the same node to eliminate ordering/warmup bias
• Wilcoxon signed-rank test (paired, non-parametric) and Mann-Whitney U test (unpaired)
• Built with patched clang (LLVM 22) on ctr2-alola-compile-11, -j1 for accurate per-TU timing
• Raw data available in Slurm job 275230 results

Test plan

• 11 unit tests added (5 for sequence_find_value, 6 for find_in_tuple_of_sequences)
• Compile-time benchmark with statistical significance (p < 0.01)
• Full CI

Tracking issue: #4229

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Generated-by: Claude Code (claude-sonnet-4-6)