[SmartSwitch] add graceful shutdown/startup utilities and visibility

[vvolam]

HLD: https://github.com/sonic-net/SONiC/blob/master/doc/smart-switch/graceful-shutdown/graceful-shutdown.md
These changes build upon enhancements in #3834

This PR adds CLI support and visibility for module-level graceful transitions (startup/shutdown/reboot) to align with the SmartSwitch/DPU lifecycle work.

What I did

• Added support to view module transition states (startup, shutdown, reboot) through CLI.
• Integrated with STATE_DB CHASSIS_MODULE_TABLE to display transition status, type, and elapsed time.
• Enhanced user experience with readable durations and exit codes for automation.
• Implemented comprehensive unit tests for transition visibility, parsing, and error handling.

How I did it

• Added a helper class to read STATE_DB entries:
  • state_transition_in_progress
  • transition_type
  • transition_start_time
• Implemented robust error handling for missing or malformed DB entries.
• Added pytest-based unit tests using mocked state_db_connector.

How to verify it

• Build and install the updated sonic-utilities package on DUT
• Check Redis entries: redis-cli -n 6 hgetall "CHASSIS_MODULE_TABLE|DPU0"
• Run the module startup/shutdown commands
• Run unit tests

Previous command output (if the output of a command-line utility has changed)

New command output (if the output of a command-line utility has changed)

[mssonicbld]

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[Copilot]

Pull Request Overview

This PR refactors module state transition tracking by moving the implementation from STATE_DB to platform-level methods. The change introduces three new methods in ModuleHelper to manage state transitions through the platform API instead of using database entries with timestamps.

• Adds set_module_state_transition, clear_module_state_transition, and get_module_state_transition methods to ModuleHelper
• Removes STATE_DB-based transition tracking functions from config/chassis_modules.py
• Updates shell script to use new platform-level transition flag management

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 7 comments.

Show a summary per file

File	Description
utilities_common/module.py	Adds three new methods for managing module state transitions via platform API
tests/test_module.py	Adds comprehensive unit tests for the new state transition methods
tests/chassis_modules_test.py	Updates tests to use platform-level transition checks instead of STATE_DB queries
scripts/reboot_smartswitch_helper	Adds shell functions to set/clear/get state transition flags via Python API
config/chassis_modules.py	Removes STATE_DB transition tracking functions and simplifies shutdown/startup logic

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