Ensure fragment views are marked for display when layout or rendering changes occur

This commit updates the NSTextViewportLayoutControllerDelegate implementation in
both AppKit and UIKit versions of STTextView to conditionally set
fragmentView.needsDisplay (or setNeedsDisplay) only when necessary. It also adds
a @Invalidating(.layout) attribute to textContainerInset to trigger layout
updates appropriately in UIKit. These changes improve rendering consistency and
performance when invisible characters or layout frames change.