test(translate): replace karma/jasmine with vitest

[spliffone]

Describe in detail what your merge request does and why. Add relevant
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[gemini-code-assist]

Summary of Changes

Hello @spliffone, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request undertakes a significant modernization of the project's testing infrastructure by transitioning from the Karma/Jasmine setup to Vitest. The changes span across configuration files, dependency management, and the actual test code, ensuring that the unit tests are fully compatible with the new, faster, and more developer-friendly Vitest environment. This move aims to streamline the testing process and enhance overall development efficiency.

Highlights

• Testing Framework Migration: The unit testing framework for the element-translate-ng project has been migrated from Karma and Jasmine to Vitest.
• Angular Configuration Update: The angular.json file has been updated to use the new @angular/build:unit-test builder, pointing to a vitest.config.ts file, and includes new ci and development configurations for testing.
• Dependency Changes: New development dependencies such as vitest, @vitest/browser-playwright, and jsdom have been introduced to support the Vitest testing environment.
• Test File Refactoring: Existing test files have been refactored to align with Vitest's testing patterns, specifically by using async/await with firstValueFrom for RxJS observables and vi.spyOn for mocking.
• Configuration Cleanup and Adjustment: The karma.conf.cjs file has been removed, and TypeScript configurations (tsconfig.lib.json, tsconfig.spec.json) have been adjusted to properly support Vitest and manage mock files.

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[gemini-code-assist]

Code Review

This pull request successfully migrates the testing framework for element-translate-ng from Karma/Jasmine to Vitest. The changes are well-executed, including updates to angular.json to use the new test runner, modifications to package.json with the necessary dependencies, and refactoring of test files to use Vitest's API and modern async/await syntax. The removal of the Karma configuration and updates to tsconfig files are also correctly handled. I have one minor suggestion for improving the clarity of the new vitest.config.ts file.