Fix SCMR failure actions marshaling and add regression test (Issue #2046)

[alexisbalbachan]

Fix scmr.RChangeServiceConfig2W() for SERVICE_CONFIG_FAILURE_ACTIONS when lpsaActions is populated. (Issue #2046)

SERVICE_FAILURE_ACTIONSW.lpsaActions was modeled as an inline structure, but the SCMR protocol defines it
as [size_is(cActions)] SC_ACTION*. That caused requests with non-empty failure actions to be marshaled incorrectly and
fail with rpc_x_bad_stub_data.

Changes:

• Model lpsaActions as a pointer to a conformant array of SC_ACTION
• Keep cActions synchronized with the pointed array during marshaling
• Added regression test

References

• MS-SCMR SERVICE_FAILURE_ACTIONSW:
  https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-scmr/58032b71-1e5c-4f2e-8545-34b0f2e8c6ad
• SC_ACTION:
  https://learn.microsoft.com/en-us/windows/win32/api/winsvc/ns-winsvc-sc_action

[Copilot]

Pull request overview

Fixes incorrect marshaling of SERVICE_CONFIG_FAILURE_ACTIONS in scmr.RChangeServiceConfig2W() when lpsaActions is non-empty, and adds a regression test to cover the failure-actions path.

Changes:

• Model SERVICE_FAILURE_ACTIONSW.lpsaActions as a pointer to a conformant array ([size_is(cActions)] SC_ACTION*).
• Synchronize cActions with the pointed action array during marshaling.
• Refactor SCMR config query logic in tests and add a dedicated regression test for failure actions.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
impacket/dcerpc/v5/scmr.py	Updates NDR modeling for failure actions to correctly represent lpsaActions as a pointer to an SC_ACTION conformant array and syncs cActions at marshal time.
tests/dcerpc/test_scmr.py	Adds query helpers and a regression test validating ChangeServiceConfig2W failure-actions behavior and round-tripping via QueryServiceConfig2W.

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