[ios][android] Update react-native-svg to 12.1.1

[brentvatne]

Why

SDK 42

How

• The latest version of react-native-svg moves the ios source code to the apple directory within their repo, which is easy enough to adjust, but the reason for the change was to add macOS support. This required writing a SvgModifier in our vendoring script to delete macOS specific source files and add a missing header import.
• The commit bumping the version to 12.1.1 was not actually pushed to the react-native-svg repo, so I had to import from the parent commit and then manually increment the version number in our repo from 12.1.0 to 12.1.1.

Test Plan

Built iOS and Android Expo Go, ran NCL on unversioned.

Checklist

• Documentation is up to date to reflect these changes (eg: https://docs.expo.io and README.md).
• This diff will work correctly for expo build (eg: updated @expo/xdl).
• This diff will work correctly for expo prebuild & EAS Build (eg: updated a module plugin).