feat(iOS): add xcassets support

[ajanuar]

Description

This PR adds support for using .xcassets asset catalog icons across key navigation UI elements. Developers can now reference native asset names directly for both bottom-tab icons and header bar button items, removing the need to bundle standalone image files. By integrating with iOS/macOS asset catalogs, the update aligns icon handling with platform best practices, simplifies asset management, and enables automatic support for multi-resolution and variant images (such as dark mode).

Addresses discussion.
Closes https://github.com/software-mansion/react-native-screens-labs/issues/576.

Usage

You can add logo to asset catalog via Xcode:

Changes

• add xcasset icon type for iOS
• handle xcasset for Tabs
• handle xcasset for Bar Button Items in Stack
• update BarButtonItems example screen and add Test3443 that tests xcassets in Bottom Tabs
  • Test3443 should be converted in the future into single feature test when chore: Refactor library examples & tests #3528 is merged

Before & after - visual documentation

Bottom Tabs	Header Bar Button Item

Menu	Submenu

Test code and steps to reproduce

Run BarButtonItems example screen. Use XcassetIconButtonDemo and AdvancedMenuButtonDemo.
Run Test3443.

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

[kkafar]

Hey! Thanks for the PR. We'll look into it after 4.19.0 release

[ajanuar]

Thank you @kkafar ! I'll add more tests

[ajanuar]

Hi @kkafar @kligarski , any chance to review this PR? Thank you

[kkafar]

Hey @ajanuar, it's in our task queue for January. We'll look into it.

[kligarski]

Hi, @ajanuar. Thanks for the PR and sorry for the delay.

I'll push some changes and modify the description a bit. Hopefully, we'll be ready to land this soon.

[kligarski]

I'm not sure about the name of this prop (iconResourceName). It's used for both sfsymbols and xcassets. We also have drawableIconResourceName and imageIconResource on Android which have very similar name.

Maybe those props should be unified (iconImageSource (removing imageIconResource), iconResourceName (removing drawableIconResourceName) for both platforms and selectedIconImageSource, selectedIconResourceName as iOS-only).

[kligarski]

I don't like this solution (adding new prop to pass xcasset's name), we could use only one prop for both sfsymbolname and xcassetname however we're currently not passing iconType so we can't differentiate between the two.

At least we're not passing it intentionally - we're using ...icon so it actually is present on the native side but I don't want to rely on that. We need to refactor this logic and add proper typing in JS layer because it's very difficult to add any changes now without being afraid of this whole feature breaking apart.

Decided to go with separate prop for now as refactoring this logic would be way out of scope of this PR.