chore: Remove dead-code from Alert module

[retyui]

Summary:

Code elimination won't be able to remove dead-code in if conditions that's always false, as Platfrom.OS === 'ios' is a runtime check

Changelog:

[GENERAL] [CHANGED] - Separate an Alert implementation per platforms to remove dead-code

Test Plan:

// Run app and do
Alert.alert(...);
Alert.prompt(...); // ios only

[github-actions]

Warning

JavaScript API change detected

This PR commits an update to ReactNativeApi.d.ts, indicating a change to React Native's public JavaScript API.

• Please include a clear changelog message.
• This change will be subject to additional review.

This change was flagged as: POTENTIALLY_BREAKING