Move user-defined passes after SpecPropPass

[lucylq]

Summary:

1. Use ExecutorchBackendConfig instead of inserting the pass.
2. Move SpecPropPass after user-defined passes. It was originally swapped here: D80840528. cc ethansfng, who has a pass that should run before SpecPropPass

Differential Revision: D87576772

[pytorch-bot]

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❌ 2 New Failures, 2 Unrelated Failures

As of commit bd92f7a with merge base b4d72f1 ():

NEW FAILURES - The following jobs have failed:

• Lint / lintrunner / linux-job (gh)
  >>> Lint for extension/llm/export/builder.py:
• pull / test-qnn-wheel-packages-linux (3.10) / linux-job (gh)
  RuntimeError: Command docker exec -t 0b9d42f4797af071914596770f4204c5e286c4dccf50decad437a82b41de42d9 /exec failed with exit code 1

FLAKY - The following job failed but was likely due to flakiness present on trunk:

• pull / unittest / linux / linux-job (gh) (detected as infra flaky with no log or failing log classifier)

BROKEN TRUNK - The following job failed but was present on the merge base:

👉 Rebase onto the `viable/strict` branch to avoid these failures

• pull / unittest-editable / linux / linux-job (gh) (trunk failure)

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[meta-codesync]

@lucylq has exported this pull request. If you are a Meta employee, you can view the originating Diff in D87576772.

[meta-codesync]

@lucylq has exported this pull request. If you are a Meta employee, you can view the originating Diff in D87576772.

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