[Feature] Add Network Inspector command tests

[ConnorQi01]

Summary

Add focused unit coverage for the Network Inspector start and stop command wrappers.

Proposed Changes

• Add tests for starting the Network Inspector when it is not already running.
• Add tests for the already-running branch to verify it logs and skips duplicate starts.
• Add tests for stopping the Network Inspector.

Test Plan

• npm run build
• node .\node_modules\mocha\bin\_mocha test\extension\networkInspector\startStopCommands.test.js --ui tdd --timeout 10000

Closes #2656