Embedded Snippets Support

What does this MR do?

This MR introduces Embedded Snippets Support. And an embed and share snippet option for a public snippet (if it a project snippet, this feature only available for public projects)

Are there points in the code the reviewer needs to double check?

this is new feature. so the way of implementation needs to double check

Why was this MR needed?

to allow embedding snippets in other websites

fix #8088 (closed)

Screenshots (if relevant)

Snippets Page

Embedded Snippet

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• API support added
• Tests added for this feature/bug
• Review
  • Has been reviewed by UX
  • Has been reviewed by Frontend
  • Has been reviewed by Backend
  • Has been reviewed by Database
• Conform by the merge request performance guides
• Conform by the style guides
• Squashed related commits together
• Internationalization required/considered

What are the relevant issue numbers?

#8088 (closed)