Manage search paths with sync_project.rb (#3326)

* xcodeproj: Remove needless FRAMEWORK_SEARCH_PATHS

* xcodeproj: Remove manually specified language standards

* Manage swift versions and bridging headers

* xcodeproj: Remove manually specified swift settings

* Manage header search paths

* xcodeproj: Remove manually specified search paths

* Manage language standards based on the podspec

Author: wilhuff