[system] Update replaced state handling

[ArunSaravananBalachandran]

SUMMARY

Incorporate the below changes in sonic_system module:

• Update replaced state handling.
• Update UT cases.

GitHub Issues

List the GitHub issues impacted by this PR. If no Github issues are affected, please indicate this with "N/A".

GitHub Issue #
N/A

ISSUE TYPE

• Bugfix Pull Request

COMPONENT NAME

• sonic_system

OUTPUT

ADDITIONAL INFORMATION

Checklist:

• I have performed a self-review of my own code to ensure there are no formatting, linting, or security issues
• I have verified that new and existing unit tests pass locally with my changes
• I have not allowed coverage numbers to degenerate
• I have maintained at least 90% code coverage
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• I have maintained backward compatibility or have provided any relevant "breaking_changes" descriptions in a "fragment" file in the "changelogs/fragments" directory of this repository.
• I have provided a summary for this PR in valid "fragment" file format in the "changelogs/fragments" directory of this repository branch. Reference : Ansible Change Log Document

How Has This Been Tested?

Please describe the tests that you ran to verify your changes. Please also list any relevant details for your test configuration

Regression report: system_regression_report.pdf

[kerry-meyer]

All proposed code changes and corresponding test results look good.

Thank you for fixing the problems with 'replaced' state handling. Thanks also for consolidating and reorganizing this code to reduce redundant instruction sequences, minimize execution time, and improve the readability and maintainability of this code.

Approved.