Summary:
The `RCTImageURLLoaderWithAttribution` protocol historically only returns a cancellation block to cancel the url request. But for more complex instrumentation, we may need to associate a requestId for the specific URL request. To do this, the protocol now returns an object that has both the unique ID and the cancellation block, so that instrumentation logic can refer to the ID in the future.
Note that the `RCTImageURLLoader` protocol is unchanged, because the request ID is only relevant for instrumentation purpose.
Changelog: [Internal]
Reviewed By: mdvacca
Differential Revision: D19047900
fbshipit-source-id: cd029f2470c32fc7bffd674b09a5353fe1dbc80b
Kevin Gozali
743074d09c