Summary:
By leveraging the `PUBLIC_HEADERS_FOLDER_PATH` build settings of Xcode, we can instruct cocoapods to generate the frameworks Headers in a specific folder, for example the `React` folder.
This allows us to maintain the `#include`/`#import` structure, even if the framework has a different name.
However, we need to update the search paths to take into account this extra folder.
## Changelog:
[iOS][Changed] - Generate RCTFabric framework's headers in the React folder
Reviewed By: sammy-SC, dmytrorykun
Differential Revision: D43425677
fbshipit-source-id: 94a4f3a3c7de86341b3ce3457704e6b8fb9a588e
e7becb06c1