[Ez][BE] Make implicit subpackage explicit

[shink]

Part of: #153546
Follow up: #153347

I run the following command to find all implicit namespace packages:

ruff check . --select INP001 | grep __init__.py

cc @malfet @seemethere @voznesenskym @penguinwu @EikanWang @jgong5 @Guobing-Chen @XiaobingSuper @zhuhaozhe @blzheng @wenzhe-nrv @jiayisunx @ipiszy @chenyang78 @kadeng @muchulee8 @amjames @chauhang @aakhundov

[pytorch-bot]

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🧪 See artifacts and rendered test results at hud.pytorch.org/pr/153613

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❌ 1 New Failure, 1 Unrelated Failure

As of commit 0c750d4 with merge base 2908c10 ():

NEW FAILURE - The following job has failed:

• pull / linux-docs / build-docs-python-false (gh)
  Process completed with exit code 1.

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

• pull / linux-jammy-py3-clang12-executorch / test (executorch, 1, 1, lf.linux.2xlarge, unstable) (gh)
  exir/backend/test/test_to_backend_multi_method.py::TestToBackendMultiMethod::test_multi_method_end_to_end

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[jerryzh168]

looks like there are failures

[shink]

Thanks for review! Have fixed.

[Skylion007]

@shink Please fix the Python docs for the package

[shink]

@pytorchbot rebase -b main

[pytorchmergebot]

@pytorchbot started a rebase job onto refs/remotes/origin/main. Check the current status here

[pytorchmergebot]

Successfully rebased fix/implicit-subpackage onto refs/remotes/origin/main, please pull locally before adding more changes (for example, via git checkout fix/implicit-subpackage && git pull --rebase)

[justinchuby]

all should be placed before imports: https://peps.python.org/pep-0008/#module-level-dunder-names

[albanD]

Why are there new entries to this file? We should not have any new entry added to this file.