Optimize text insertion using textStorage for better performance and …

[SPStore]

• Fixed textView flickering issue when typing multiple lines of @mentions: This issue was caused by setting textView.attributedText = NSAttributedString().
• Fixed the issue: deleting all the spaces between two @mentions using backspace, continuing to delete either of the @mentions causes both @mentions to be deleted together.
• Supports inserting @mentions at any position, not just at the end of the text.
• Replaced UITableView with UICollectionView
• Supports multiple consecutive @mentions
• Supports horizontal scrolling functionality.

Explanation for the change: In this commit, I replaced UITableView with UICollectionView, which is a more flexible and modern solution. This change provides better support for features like multiple layouts and horizontal scrolling. However, it is not compatible with older versions of the app, as UITableView has been completely removed. I want to make sure the team is aware that this change removes backward compatibility with older versions. This may cause issues for users on previous versions, as they will no longer have access to the old UITableView functionality. Please review this change and consider the potential impact on legacy users

https://github.com/user-attachments/assets/10849a13-0157-494d-ab6c-8a9986034fba

[Kaspik]

The amount of changes is huge against original PR, so I'm not merging this.