Add sagemaker unit tests to main

[vpaiu]

Issue

D356921475

Description of Changes

• Fetched the sagemaker unit tests from: Add testing changes sagemaker-code-editor#202
• Tweaked the following unit tests because of patch differences:
  1. webview.test.ts - Updated the hashes.
  2. custom-extensions-marketplace.test.ts - Changed because Code Editor has its own patch for custom marketplace (patches/web-server/marketplace.diff)
  3. signature-verification.test.ts - Removed some tests which are unnecessary because of patches/common/allow-unused-vars.diff
  4. display-language.test.ts - Rewrote the unit tests to fit Code Editor's patches/web-server/display-language.diff patch.
• Imported the script for running the unit tests with one small change: the script now checks if the code-editor-src folder exists, if it doesn't ./scripts/prepare-src.sh code-editor-sagemaker-server is executed.
• Made changes to .gitignore for ignoring the node_modules, package.json, and package-lock.json generated during the tests run.
• Changed the CODEOWNERS file to allow the sagemaker team to make changes to the sagemaker-tests folder.

Testing

The unit tests all run successfully locally

Screenshots/Videos

N/A

Additional Notes

N/A

Backporting

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.