Support React Native 0.71 (#2313)

## Description

This PR adds support for new architecture on React Native 0.71, which
most notably includes the usage of prefabs in native builds.

It also removes most of the dependencies of `FabricExample` app, so
upgrades in the future should be easier.

Co-authored-by: Kacper Kafara <[email protected]>

Author: j-piasecki

FabricExample/.buckconfig

@@ -31,19 +31,15 @@ local.properties
 *.iml
 *.hprof
 .cxx/
+*.keystore
+!debug.keystore
 
 # node.js
 #
 node_modules/
 npm-debug.log
 yarn-error.log
 
-# BUCK
-buck-out/
-\.buckd/
-*.keystore
-!debug.keystore
-
 # fastlane
 #
 # It is recommended to not store the screenshots in the git repo. Instead, use fastlane to re-generate the
@@ -62,3 +58,6 @@ buck-out/
 # Ruby / CocoaPods
 /ios/Pods/
 /vendor/bundle/
+
+# Temporary files created by Metro to check the health of the file watcher
+.metro-health-check*

FabricExample/.flowconfig

@@ -1,6 +1,6 @@
 source 'https://rubygems.org'
 
 # You may use http://rbenv.org/ or https://rvm.io/ to install and use this version
-ruby '2.7.5'
+ruby File.read(File.join(__dir__, '.ruby-version')).strip
 
-gem 'cocoapods', '~> 1.11', '>= 1.11.2'
+gem 'cocoapods', '~> 1.11', '>= 1.11.3'

FabricExample/.gitignore

@@ -0,0 +1 @@
+16

FabricExample/Gemfile

@@ -1 +1 @@
-2.7.5
+2.7.6