Add more unittest command

[pan-x-c]

Description

• /unittest-all: Run all unit-tests
• /unittest-diff: Check for changed modules and run tests in those modules
• /unittest-module-xxx: Run tests in xxx module

Checklist

Please check the following items before code is ready to be reviewed.

• Code has passed all tests
• Docstrings have been added/updated in Google Style
• Documentation has been updated
• Code is ready for review

[gemini-code-assist]

Note

Gemini is unable to generate a summary for this pull request due to the file types involved not being currently supported.

[Copilot]

Pull Request Overview

This PR adds new unittest command options for GitHub Actions workflows, expanding from a single /run-unittest command to multiple test execution modes including running all tests, running tests for changed modules only, and running tests for specific modules.

• Adds three new unittest command variants: /unittest-all, /unittest-diff, and /unittest-module-xxx
• Implements logic to detect test type from comment body and execute appropriate test strategy
• Adds functionality to identify changed modules and run only relevant tests for diff mode