Add new filters to SnippetsFinder

What does this MR do?

In #36079 (closed), we're going to need some more filters to the SnippetsFinder, specifically:

• Filter by id
• Allow author to be an id and not only an object
• Allow project to be an id and not only an object
• Allow filtering only PersonalSnippet
• Allow filtering only ProjectSnippet

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