Arm backend: Annotate maximum/minimum ops w. independent observers

[AdrianLundell]

Previous shared observers meant that inputs and outputs were all quantized within the same range. In cases where the output is heavily truncated, this left a lot of the output range unused, leading to unnecessarily poor accuracy.

cc @digantdesai @SS-JIA @freddan80 @per @zingo @oscarandersson8218 @mansnils @Sebastian-Larsson @robell

[pytorch-bot]

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❌ 1 Awaiting Approval, 10 New Failures, 12 Pending

As of commit 22f7610 with merge base 122fdef ():

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• periodic (gh)

NEW FAILURES - The following jobs have failed:

• pull / android / build-android (gh)
  Process completed with exit code 1.
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t c081d919d4e7621afbf72c13b1ccd9ca4e0d7178b384aa51405e70180f032a41 /exec failed with exit code 1
• pull / test-samsung-quantmodels-linux / linux-job (gh)
  RuntimeError: Command docker exec -t e0ae157fc734b258e7f7f2db301ae5287dc91488724bc4571dd313ffdae17c3a /exec failed with exit code 1
• pull / unittest-editable / macos / macos-job (gh)
  export/tests/test_target_recipes.py::TestTargetRecipes::test_linear_model
• trunk / test-llama-runner-qnn-linux (fp32, qnn_16a16w, qnn) / linux-job (gh)
  RuntimeError: Command docker exec -t a2968c92b4367756d4ce2d99202d0a3af5f34558b8b1cf816df5803870b07358 /exec failed with exit code 92
• trunk / test-qnn-model (fp32, ic4) / linux-job (gh)
  RuntimeError: Command docker exec -t 5d8474ea0218dd924616a7814b92ae9e1612045ba58ca6630f397149c02d1897 /exec failed with exit code 92
• trunk / test-qnn-model (fp32, mv2) / linux-job (gh)
  RuntimeError: Command docker exec -t 79f68f369a57b9ae6366a5dd6a58efc93070aab8daa90e6c8eae25fb348f40a6 /exec failed with exit code 92
• trunk / test-qnn-model (fp32, mv3) / linux-job (gh)
  RuntimeError: Command docker exec -t e1e637f4f60a50c6f613ce16e73cda134b6ba8e0d15dcbd587be7874d45a0dda /exec failed with exit code 92
• trunk / test-qnn-optimum-model (fp32, dit) / linux-job (gh)
  RuntimeError: Command docker exec -t 3a59286fd50f794183c05038278e3199642cfcd5fdbf017743a59343077dae5f /exec failed with exit code 9
• trunk / test-qnn-optimum-model (fp32, swin) / linux-job (gh)
  RuntimeError: Command docker exec -t 876c4960383d901f48e7c5baa6250ed133803315b387f73464671a2bede0901d /exec failed with exit code 92

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