feat: add Fabric on iOS without ComponentViews (#1821)

Version of #1754 without usage of ComponentViews. It seems like a more proper way, but introduces the necessity of clearing whole state of each component on recycling for it not to be used when view is recycled.

Still known problems:

We stringify props of type NumberProp since codegen only accepts props of a single type. It is the fastest way of dealing with it, but maybe there could be a better way to handle it.
Image resolving should be probably handled the same as in RN core
SvgView needs to set opaque = NO so it is does not have black background (it comes from the fact that RCTViewComponentView overrides backgroundColor setter which in turn somehow messes with the view being opaque). All other svg components do it already so maybe it is not such an issue.
transform prop won't work when set natively since it is not parsed in Fabric

FabricExample/ios/Podfile

@@ -0,0 +1,39 @@
+require_relative '../node_modules/react-native/scripts/react_native_pods'
+require_relative '../node_modules/@react-native-community/cli-platform-ios/native_modules'
+
+platform :ios, '11.0'
+install! 'cocoapods', :deterministic_uuids => false
+
+ENV['RCT_NEW_ARCH_ENABLED'] = '1'
+
+target 'FabricExample' do
+  config = use_native_modules!
+
+  # Flags change depending on the env values.
+  flags = get_default_flags()
+
+  use_react_native!(
+    :path => config[:reactNativePath],
+    # to enable hermes on iOS, change `false` to `true` and then install pods
+    :hermes_enabled => flags[:hermes_enabled],
+    :fabric_enabled => flags[:fabric_enabled],
+    # An absolute path to your application root.
+    :app_path => "#{Pod::Config.instance.installation_root}/.."
+  )
+
+  target 'FabricExampleTests' do
+    inherit! :complete
+    # Pods for testing
+  end
+
+  # Enables Flipper.
+  #
+  # Note that if you have use_frameworks! enabled, Flipper will not work and
+  # you should disable the next line.
+  use_flipper!()
+
+  post_install do |installer|
+    react_native_post_install(installer)
+    __apply_Xcode_12_5_M1_post_install_workaround(installer)
+  end
+end