Add support for seq at dim=2

[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

This makes custom sdpa and quantized sdpa on feature parity
and allows for transposed kv cache

Differential Revision: D93870394

[pytorch-bot]

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❌ 13 New Failures, 2 Cancelled Jobs

As of commit ffb29f7 with merge base fb1618e ():

NEW FAILURES - The following jobs have failed:

• pull / test-llama-runner-linux (bf16, custom, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh)
  AttributeError: 'SDPACustom' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh)
  AttributeError: 'SDPACustom' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+custom+qe, linux.arm64.2xlarge, executorch-ubuntu-22.04-gc... / linux-job (gh)
  AttributeError: 'SDPACustom' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+custom+quantize_kv, linux.2xlarge, executorch-ubuntu-22.04... / linux-job (gh)
  AttributeError: 'QuantizedSDPA' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+custom+quantize_kv, linux.arm64.2xlarge, executorch-ubuntu... / linux-job (gh)
  AttributeError: 'QuantizedSDPA' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+quantize_kv, linux.2xlarge, executorch-ubuntu-22.04-clang12) / linux-job (gh)
  AttributeError: 'QuantizedSDPA' object has no attribute 'is_seq_at_dim_2'
• pull / test-llama-runner-linux (fp32, xnnpack+quantize_kv, linux.arm64.2xlarge, executorch-ubuntu-22.04-... / linux-job (gh)
  AttributeError: 'QuantizedSDPA' object has no attribute 'is_seq_at_dim_2'
• pull / test-lora-linux / linux-job (gh)
  AttributeError: 'SDPACustom' object has no attribute 'is_seq_at_dim_2'
• pull / test-lora-multimethod-linux / linux-job (gh)
  AttributeError: 'SDPACustom' object has no attribute 'is_seq_at_dim_2'
• pull / unittest / linux / linux-job (gh)
  examples/models/llama/tests/test_export_llama_lib.py::ExportLlamaLibTest::test_has_expected_ops_and_op_counts
• pull / unittest / macos / macos-job (gh)
  examples/models/llama/tests/test_export_llama_lib.py::ExportLlamaLibTest::test_has_expected_ops_and_op_counts
• pull / unittest-editable / linux / linux-job (gh)
  examples/models/llama/tests/test_export_llama_lib.py::ExportLlamaLibTest::test_has_expected_ops_and_op_counts
• pull / unittest-editable / macos / macos-job (gh)
  examples/models/llama/tests/test_export_llama_lib.py::ExportLlamaLibTest::test_has_expected_ops_and_op_counts

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