Remove unused functions for quantization handling

[per]

Remove functions not used for searching/finding quantization information.

cc @digantdesai @freddan80 @zingo @oscarandersson8218

[pytorch-bot]

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❌ 2 New Failures, 3 Cancelled Jobs

As of commit 0d4abcc with merge base d1b33cb ():

NEW FAILURES - The following jobs have failed:

• pull / unittest / macos / macos-job (gh)
  backends/xnnpack/test/ops/test_add.py::TestAdd::test_qs8_add_relu_seq
• trunk / test-arm-backend-delegation / linux-job (gh)
  AttributeError: 'ArmCompileSpecBuilder' object has no attribute 'set_quantize_io'

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

• trunk / test-llama-runner-mac (fp32, coreml) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-llama-runner-mac (fp32, xnnpack+kv+custom) / macos-job (gh)
  ##[error]The operation was canceled.
• trunk / test-models-macos (cmake, emformer_join, xnnpack-quantization-delegation, macos-m1-stable, 90) / macos-job (gh)
  ##[error]The operation was canceled.

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[zingo]

Probably just need to be rebased as set_quantize_io() was removed in d1b33cb
(merged a short while ago)