Add ScriptImporter URL unit tests

[ConnorQi01]

Summary

• Add focused unit tests for ScriptImporter debugger worker URL construction across legacy, debugger UI, canary, and explicit path cases.
• Include the new ScriptImporter test in the VS Code test runner without enabling the full debugger test directory.
• Cover packager port replacement while preserving URL query strings.

Test Plan

• npx gulp format
• npx tsc --noEmit
• npm test (ScriptImporter tests passed; existing unrelated settings/android tests failed with timeout/channel-closed errors)

Closes #2716

[ConnorQi01]

/azp run

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[ConnorQi01]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).