fix: forward extraData to the documented getItemType callback

[OskarEichler]

Fix

• pass the current extraData as the documented third argument of getItemType
• add a focused regression that exercises the real layout-manager call path

Problem

FlashListProps documents getItemType(item, index, extraData), but RecyclerViewManager supplied only the first two arguments. Callbacks using the documented third argument therefore received undefined during layout and recycling.

Compatibility / observable changes

No signature change. Callbacks now receive their documented third argument. This PR does not claim that changing only extraData reassigns every existing recycled cell; that is a separate behavior and is intentionally excluded.

Verification

• regression fails on untouched main and passes with this fix
• full Jest suite: 14 suites, 188 tests passed
• library TypeScript check passed
• changed-file ESLint and git diff --check passed
• no dependency, lockfile, native SDK, or Songstats application change

Reviewers’ hat-rack 🎩

• Check the stated compatibility behavior and focused regression.
• Run the existing test/type/lint commands on a supported environment.

[OskarEichler]

I have signed the CLA!