Summary:
**Note:** This was landed in D17722913, but reverted in D17855088. The revert had nothing to do with this NativeModule.
Changelog: [iOS][Added] Make RCTAlertManager TurboModule-compatible
Reviewed By: PeteTheHeat
Differential Revision: D17917827
fbshipit-source-id: d86ea2cddddd9535d656709296c74aebd6f45793