Add support for transposed kv cache in all variants of custom kv cache

[kimishpatel]

Stack from ghstack (oldest at bottom):

• temp changes to enable benchmarking on device via adb #18719
• Add xplat cxx_binary target for bench_transposed_cache benchmark #18718
• Add non-flash SDPA path gated by ET_USE_UNFUSED_SDPA #18717
• Add ONNX Runtime GQA-style SDPA benchmark #18716
• Add GEMM-based standard SDPA benchmark and fix custom_sdpa_out signature #18715
• Support separate K/V seq dim in custom_sdpa op #18714
• Add --no_transposed_cache CLI flag for export pipeline #18713
• Plumb transposed cache config through export pipeline #18712
• Add benchmarks for transposed vs standard KV cache layout #18711
• temp hack #18710
• -> Add support for transposed kv cache in all variants of custom kv cache #18709
• Add contig requirement to aot binding for llm custom ops #18708
• Add support for seq at dim=2 #18707
• Make kv cache update op support transposed cache #18706
• Add xplat cxx_binary target for bench_sdpa #18705
• Use unfused SDPA for short sequences (q_len <= 128 or kv_len <= 128) #18651
• Limit softmax to causally-valid elements in cpu_sdpa #18650
• Add quantized input support to cpu_sdpa #18649
• [Executorch] Add non-flash SDPA for decode #18648
• Add ONNX Runtime GQA-style SDPA benchmark #18647
• Add GEMM-based standard SDPA benchmark #18646
• Fix SLEEF preprocessor macro name to match ATen vec headers #18645

Differential Revision: D93870395

[pytorch-bot]

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❌ 12 New Failures, 2 Cancelled Jobs

As of commit bab3440 with merge base fb1618e ():

NEW FAILURES - The following jobs have failed:

• pull / android / build-android (gh)
  Process completed with exit code 1.
• pull / test-llama-runner-linux (bf16, custom, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh)
  RuntimeError: Command docker exec -t d614aedd934356e865fa991380f661a0e0fb03b32ea65ebda6a7ea05d60fb791 /exec failed with exit code 134
• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh)
  RuntimeError: Command docker exec -t d5abb155cb9b815e61578647771658b2dbc23c0bcef807a13a21b3869e222d66 /exec failed with exit code 134
• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.arm64.2xlarge, executorch-ubuntu-22.04-gc... / linux-job (gh)
  RuntimeError: Command docker exec -t 00b077dd30be8cee73e177c6be62f9eb654b06af1a0f757a617736e8b9f70e36 /exec failed with exit code 134
• pull / test-lora-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 5a7117fab31dc7fd5b40af8a2f751b025914caf9149689a230873dac241415bc /exec failed with exit code 134
• pull / test-lora-multimethod-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 728b6ae556bd71093db0e0f9178a5ce766238bde7d80263896f294370690a0e0 /exec failed with exit code 134
• pull / test-multimodal-linux (gemma3-4b) / linux-job (gh)
  RuntimeError: Command docker exec -t 16c0d96ec88c7a94fe4ed671a1455c9a6d31db4c6fc2c74180dd37c3316bf196 /exec failed with exit code 134
• pull / unittest / linux / linux-job (gh)
  examples/models/llama/tests/test_replace_kv_cache.py::TestReplaceKVCache::test_replace_quantized_kv_cache_with_quantized_ring_kv_cache
• pull / unittest / macos / macos-job (gh)
  examples/models/llama/tests/test_replace_kv_cache.py::TestReplaceKVCache::test_replace_quantized_kv_cache_with_quantized_ring_kv_cache
• pull / unittest-buck / macos / macos-job (gh)
  RuntimeError: Command bash /Users/ec2-user/runner/_work/_temp/exec_script failed with exit code 1
• pull / unittest-editable / linux / linux-job (gh)
  examples/models/llama/tests/test_replace_kv_cache.py::TestReplaceKVCache::test_replace_quantized_kv_cache_with_quantized_ring_kv_cache
• pull / unittest-editable / macos / macos-job (gh)
  examples/models/llama/tests/test_replace_kv_cache.py::TestReplaceKVCache::test_replace_quantized_kv_cache_with_quantized_ring_kv_cache

CANCELLED JOBS - The following jobs were cancelled. Please retry:

• pull / unittest / windows / windows-job (gh)
• pull / unittest-editable / windows / windows-job (gh)

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[kimishpatel]

submitted by accident, not meant to land immedidately