feat: use prebuilt React Native for iOS

[radoslawrolka]

Description

Speed up the build process from ~6min to ~3min (macos-xlarge-latest)

I briefly checked debugging and it seems that debug symbols aren't available in XCode - meaning that for some more advanced debugging sessions we'd have to locally rollback to building from source.

If this change proves to be counterproductive we can revert it later. It will significantly speed up the builds on CI, in local development it can be easily switched off

same in react-native-reanimated: software-mansion/react-native-reanimated#8983

Changes

• Enabled uising prebuilt react-native via env variables in Podfile

Test plan

build FabricExample and try to debug something

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, as you can see in the Podfile, we've explicitly disabled the prebuilt. FabricExample is the main application where we do lib testing & development, which very often requires us to add patch / logs & debug RN behaviour.

I won't accept the change in this form - it will be counterproductive.

What I can agree for is prebuilt configured for CI only, e.g. by verifying that RCT_USE_PREBUILT_RNCORE is explicitly set to 1 in the env.