Qualcomm AI Engine Direct - Adding QNN backend support for randn core ATen op

[qti-horodnic]

Summary

Added support for the randn core ATen op using the existing QNN backend implementation of RandomNormalLike. Note only INT8 outputs are supported.

Also fixed a minor bug in the rand op's implementation and test.

Test plan

python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNQuantizedOperator.test_qnn_backend_randn --model 
SM8750 --host aisw-vm15-labsd --device 545ee4aa --build_folder build-android
python backends/qualcomm/tests/test_qnn_delegate.py -k TestQNNFloatingPointOperator.test_qnn_backend_randn --model SM8750 --host aisw-vm15-labsd --device 545ee4aa --build_folder build-android

[pytorch-bot]

🔗 Helpful Links

🧪 See artifacts and rendered test results at hud.pytorch.org/pr/pytorch/executorch/19377

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⚠️ 11 Awaiting Approval

As of commit 45124e6 with merge base 74c7c91 ():

AWAITING APPROVAL - The following workflows need approval before CI can run:

• Build documentation (gh)
• Build Presets (gh)
• Cadence Build & Test (gh)
• Lint (gh)
• periodic (gh)
• pull (gh)
• Test ARM Backend (gh)
• Test CoreML Backend (gh)
• Test QNN Backend (gh)
• Test Vulkan Backend (gh)
• Test XNNPACK Backend (gh)

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[qti-horodnic]

@pytorchbot label "release notes: qualcomm"