Delete unused code in tests

[JasonYeMSFT]

This PR adds a new ESLint plugin with rules to detect duplicate imports and unused exports.

• If a module is imported, there can be only one import statement for it.
• If a module is exported, another module other than itself must use it.

I removed the export operator from the unused exports detected and then removed the unused code revealed.

[Copilot]

Pull request overview

This PR cleans up unused test utilities/exports and tightens linting by adding eslint-plugin-import (including a rule to surface unused exports), then removing code that becomes unused as a result.

Changes:

• Add eslint-plugin-import to the tests ESLint flat config and enable import/no-unused-modules (unused exports) as a warning.
• Remove unused exports/utility functions across tests/utils/** (e.g., fixture helpers, unused detectors, unused wrapper factories).
• Consolidate several duplicate import statements in integration tests.

Reviewed changes

Copilot reviewed 19 out of 20 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/utils/trigger-matcher.ts	Removes unused exported types/helpers and minor formatting cleanup.
tests/utils/skill-loader.ts	Removes unused exported helpers and narrows exported surface area.
tests/utils/regression-detectors.ts	Removes unused detector functions and trims unused imports.
tests/utils/git-clone.ts	Makes an internal options type non-exported.
tests/utils/fixtures.ts	Deletes unused fixtures utility module.
tests/utils/evaluate.ts	Removes an unused exported helper and reformats types.
tests/utils/agent-runner.ts	Removes unused exports (deploy link helper + multi-turn conversation runner).
tests/package.json	Adds eslint-plugin-import.
tests/package-lock.json	Locks new dependency tree for the lint plugin (and updated transitive deps).
tests/microsoft-foundry/integration.test.ts	Consolidates imports from evaluate.
tests/microsoft-foundry/foundry-agent/create/integration.test.ts	Consolidates imports from evaluate.
tests/eslint.config.mjs	Adds eslint-plugin-import flat configs + enables import/no-unused-modules.
tests/azure-validate/utils.ts	Removes an unused helper and trims related comment text.
tests/azure-validate/integration.test.ts	Consolidates imports from evaluate.
tests/azure-resource-visualizer/integration.test.ts	Consolidates imports from evaluate.
tests/azure-rbac/integration.test.ts	Consolidates imports from evaluate.
tests/azure-prepare/integration.test.ts	Consolidates imports from evaluate.
tests/azure-messaging/integration.test.ts	Consolidates imports from evaluate.
tests/azure-hosted-copilot-sdk/util.ts	Makes internal helper functions non-exported.
tests/.eslintrc	Adds a legacy ESLint config file intended to ignore jest.config.ts.

Files not reviewed (1)

• tests/package-lock.json: Language not supported

[saikoumudi]

can we have a way to prevent duplicate imports going forward? maybe by enabling import/no-duplicates