chore: migrate eslint-plugin-import to eslint-plugin-import-x

[JounQin]

Description

close #4411

cc @escapedcat

Motivation and Context

Checklist:

• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.

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[Copilot]

Pull Request Overview

This PR migrates ESLint’s import plugin from eslint-plugin-import to eslint-plugin-import-x and updates related configurations, and also adjusts test-environment dependencies.

• Remove eslint-plugin-import and compatibility shim, add eslint-plugin-import-x and its TypeScript resolver
• Update eslint.config.mjs to use the new plugin prefixes and flat config
• In the test-environment package, remove Jest environment and add Vitest

Reviewed Changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated no comments.

File	Description
package.json	Drop eslint-plugin-import & @eslint/compat, add import-x deps
eslint.config.mjs	Swap import-plugin rules and imports to import-x equivalents
@packages/test-environment/package.json	Remove Jest env, add Vitest as a dependency

Comments suppressed due to low confidence (2)

@packages/test-environment/package.json:34

• [nitpick] Vitest was added as a test dependency, but there are no updates to test scripts or CI configurations. Consider adding or updating test entries to ensure Vitest runs correctly.

    "vitest": "^3.0.0"

eslint.config.mjs:25

• The @eslint/compat dependency was removed from package.json but compat.extends(...) remains in the config. Re-add @eslint/compat or remove the compat.extends call to avoid configuration errors.

	...compat.extends('eslint:recommended', 'prettier'),