Fix MISRA C 2012 deviations

[chinglee-iot]

Description

Fix MISRA C 2012 deviations

In this PR:

• Adding "UNITTEST" and "COV_ANALYSIS" to align FreeRTOS libraries design
• Fix rule 12.3 not to use comma operator
• Fix rule 13.4 not to use the returned value of the assignment operator
• Fix rule 17.7 for unused return value
• Fix rule 18.4 not to use arithmetic on pointer type
• Fix rule 2.2 to remove overwritten initialized value
• Fix forward NULL warning

Test Steps

Build coverity_analysis project with coverity 2023.6.1 should show no MISRA deviations.

Checklist:

• I have tested my changes. No regression in existing tests.
• I have modified and/or added unit-tests to cover the code changes in this Pull Request.

Related Issue

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