iOS 26: update Collection component

[yexingsha]

Aside from the common changes, these changes should also be applied both in iOS and iPadOS:

• Reduce the gap between icon and title to 12px.
• Increase the inset of each sub level to 16px.
• Change the appearance of the trailing number so that it uses body and secondaryLabel, and no background.

And these changes are iPadOS only, to conform with the sidebar style:

• Rows are inset 16px from the sidebar edge.
• Keep 44px row height.
• No separators needed.
• Active row uses fully rounded tertiarySystemFill background, and sets text to accent color and emphasized.