Refactor: Move Bookmarks into Dedicated Package

[lucapirolo]

• Relocated all bookmarks-related code to a new 'bookmarks' package.
• Updated references from 'neo4j.Bookmarks' to 'bm.Bookmarks' for clarity and to avoid conflicts.
• Adopted 'bm' as a package alias to resolve naming conflicts in functions, like in 'cleanupBookmarks(bookmarks bookmarks.Bookmarks)', to prevent ambiguity.
• Added Bookmarks aliases in the neo4j package to maintain backward compatibility.
• Renamed 'bookmarkManager' to 'DefaultBookmarkManager' for clearer representation and to avoid naming conflicts.

https://github.com/neo4j/neo4j-go-driver/discussions/433

[lucapirolo]

Hey @StephenCathcart. Could you let me know why the CI is failing on this PR incase its an issue with the code in that case i can fix it.