Have cocoapods rebuild FacebookSDKStrings.bundle so xcode processes strings files (#1713)

Summary:
The end result is the final product ends up converting the strings files from the current text format to a minified binary plist format.

Size change:
Before
246,293 bytes (365 KB on disk)

After
133,039 bytes (184 KB on disk)

Nice ~100KB win for installed app size.

I decided to leave the bundle alone instead of breaking out the strings into their own folder because I didn't know if anything else was using the bundle currently. It doesn't look like spm is using it, which is probably a bug.

Also I'm not sure if these strings have test coverage or not, but if not I can help make sure various translations are still working correctly. Not sure where exactly these strings are used.

To help us review the request, please complete the following:

- [x] sign [contributor license agreement](https://code.facebook.com/cla)
- [x] I've ensured that all existing tests pass and added tests (when/where necessary) Wasn't sure how to run them all, I assume PR process has CI that will run them.
- [x] I've updated the documentation (when/where necessary) and [Changelog](CHANGELOG.md) (when/where necessary)
- [x] I've added the proper label to this pull request (e.g. `bug` for bug fixes) I can't add labels.

Pull Request resolved: #1713

Test Plan:
Create a new iOS project called `CocoaPodsTranslations` and point to the local pods:

```
// Podfile

target 'CocoaPodsTranslations' do
  # Comment the next line if you don't want to use dynamic frameworks
  use_frameworks!

  # Pods for CocoaPodsTranslations
  pod 'FBSDKCoreKit', :path => '/Users/joesusnick/fbsource/fbobjc/ios-sdk'
  pod 'FBSDKLoginKit', :path => '/Users/joesusnick/fbsource/fbobjc/ios-sdk'

end
```

Adds localizations for a few languages by hitting the '+' under Localization in the project settings. (You'll need to make sure something is checked in the boxes so just accept whatever the default suggestions are)

Then change the schemes's locale in the 'edit scheme' as shown in the video and run.

{F609517560}

Complete flow to show logout alert dialog:

{F609518875}

Reviewed By: khp

Differential Revision: D27881169

Pulled By: joesus

fbshipit-source-id: 0dcb3d641e639a229020012a8b54ee7248ce9098

Author: cltnschlosser

CHANGELOG.md

@@ -9,6 +9,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 
 ### Important
 
+**Performance Improvements**
+
+- Cocoapods: FBSDKCoreKit rebuilds FacebookSDKStrings.bundle so xcode processes the strings files into binary plist format. This strips comments and saves ~181KB in disk space for apps. [#1713](https://github.com/facebook/facebook-ios-sdk/pull/1713)
+
 [Full Changelog](https://github.com/facebook/facebook-ios-sdk/compare/v9.2.0...HEAD)
 
 ## 9.2.0

FBSDKCoreKit.podspec

@@ -57,7 +57,7 @@ Pod::Spec.new do |s|
                              'FBSDKCoreKit/FBSDKCoreKit/GraphAPI/*.h'
     ss.private_header_files = 'FBSDKCoreKit/FBSDKCoreKit/Internal/**/*.h',
                               'FBSDKCoreKit/FBSDKCoreKit/AppEvents/Internal/**/*.h'
-    ss.resources = 'FacebookSDKStrings.bundle'
+    ss.resource_bundles = { 'FacebookSDKStrings' => ['FacebookSDKStrings.bundle/**/*.strings'] }
     ss.library = 'c++', 'stdc++'
   end
 end