Fix yaml support for monaco-editor with vite

What does this MR do and why?

Fix yaml support for monaco-editor with vite

• import worker manually
• add tests

Changelog: changed

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Build	Before	After
Vite
Webpack		No change

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Upload a GitLab Ultimate license to your GDK
2. Navigate to a project/group => Secure => Policies => New policy => Scan execution policy => yaml mode
3. Verify there is schema information when hovering over keys.
4. Verify there is underlining indicating warnings
5. Create a policy
6. In the security policy project that the yaml is saved in, navigate to that file (e.g. security policy project => .gitlab/security-policies/policy.yml) and edit it using Edit single file
7. Verify there is schema information when hovering over keys.
8. Verify there is underlining indicating warnings

Related to #423851

Related to #461252 (closed)