Default to using edge_program state dict if quantization data not available

[JakeStevens]

Summary:
PR #16901 added logic to replace FakeTensors with actually quantization data.

The docstring says:

        :param post_quantization_state_dict: State-dict of the model right after quantization. During partitioning, the
                                              `edge_program` only contains fake tensors without any data. In this case,
                                              this state dict is used instead (if provided). Notice: It may potentially
                                              contain outdated data,

with the key part being if provided. However, this is not the actual functionality.

By not falling back, this introduces a regression for depthwise convolutions, which have a "no dynamic" constraint that is triggered by this missing information.

This PR restores the original behavior if quantization data is not provided.

Differential Revision: D93253828

cc @robert-kalmar @digantdesai

[pytorch-bot]

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❌ 3 New Failures, 1 Cancelled Job

As of commit 34e7a93 with merge base c12dc35 ():

NEW FAILURES - The following jobs have failed:

• pull / test-llama-runner-linux (fp32, xnnpack+quantize_kv, linux.arm64.2xlarge, executorch-ubuntu-22.04-... / linux-job (gh)
  RuntimeError: Command docker exec -t eb0c11ab833bb758c56fe20580192d687f1b8374482a1d9c0bf33a87b6fe4fb3time="2026-02-13T19:30:00Z" level=error msg="error waiting for container: context canceled" /exec failed with exit code 1
• pull / test-samsung-models-linux / linux-job (gh)
  RuntimeError: Command docker exec -t de4e8e3e7f5da7f5c387a641f811b6c8a80ce8bd89055a35022f80a12d792b18 /exec failed with exit code 1
• pull / test-samsung-quantmodels-linux / linux-job (gh)
  RuntimeError: Command docker exec -t ba198ce265a8fee63f2d26b41a58275df6012f024df8fa61480904704a394daa /exec failed with exit code 1

CANCELLED JOB - The following job was cancelled. Please retry:

• periodic / gather-models (gh)

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[meta-codesync]

@JakeStevens has exported this pull request. If you are a Meta employee, you can view the originating Diff in D93253828.

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