Include create_personal_snippet ability for new/create snippet actions

What does this MR do?

In this MR we check the create_personal_snippet ability whenever we show the button to create a new snippet. It also changes the place the ability is created to avoid scoping it inside a Snippet.

Refs #37436 (closed)

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content