Arm backend: Fix two control flow bugs

[Erik-Lundell]

Arm backend: Regularize submodules before processing them.

Add a function _regularize_submodule that contains special
handling needed for submodules. This mainly solves two problems:
- Buffers in submodules are (currently) handled differently depending
  on whether they are from tracing or added in passes. The old solution
  tried avoiding having to add a new meta field, but was brittle.
  The new solution simply marks all all placeholders before passes.
- The pass pipeline assumes the dim_order of inputs and outputs to match
  the actual dim_order (tosa_dim_order). We need to ensure this.

---

Arm backend: Fix while quantization

The output of the while loop body can either re-enter
the body, or exit the while loop. Therefore, A and B
in the diagrambelow need to share the same quantization parameters.
A -> while ( RESCALE -> ... -> RESCALE -> ) -> B

Earlier tests happened to get equal qparams on the
input and output, but this is not the general case.

cc @freddan80 @per @zingo @oscarandersson8218 @digantdesai

[pytorch-bot]

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❌ 4 New Failures, 1 Unrelated Failure

As of commit 4401fbb with merge base 1cb85ef ():

NEW FAILURES - The following jobs have failed:

• pull / test-openvino-linux / linux-job (gh)
  RuntimeError: Command docker exec -t 0dbd1c805616fe61cde648878820b686deac777bf4a9e571a6ae4bd026e179a8 /exec failed with exit code 1
• Test CUDA Builds / check-all-cuda-builds (gh)
  Process completed with exit code 1.
• Test CUDA Builds / test-executorch-cuda-build-13.0 / linux-job (gh)
  RuntimeError: Command docker exec -t b1659747c151c144d31f202abca4ed97467ec4c12bc788f09ddabf3f3315b560 /exec failed with exit code 1
• trunk / test-qnn-optimum-model (fp32, dit) / linux-job (gh)
  RuntimeError: Command docker exec -t d28b838b6195bd47bfe9a97782fdd453f468a38599bace1c1d1602a7f43436c5 /exec failed with exit code 9

UNSTABLE - The following job is marked as unstable, possibly due to flakiness on trunk:

• pull / android / run-emulator (gh) (#16137)
  Timeout waiting for emulator to boot.

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[Erik-Lundell]

Failures unrelated. Should be a safe merge.