high processing latency when running in react-native

[AmitShah]

Background: There is a high latency when engine.onMessage is called from a device.The RN debugger masks the issue as calls are delegated to the chrome js engine which can perform these crypto function calls rapidly. With debugger disabled, we can track the issue.

Problem: With profiling, it was determined that the getter method "from()" for message.SIgnedMessage class is not caching the calculated ethAddress value from the signature and thus calling _recoverAddress multiple times in the lifecycle.

Solution: Implementing caching of this property changes the processing latency from 1.3s to <400 ms. So consider updating the class to reflect the caching strategy.

Enhancements: To further improve on this we should adopt my ported native ECDSA methods from bitcoin-core and write our own custom wrapper.

[AmitShah]

create a react-native js wrapper for this: https://github.com/AmitShah/ios-secp256k1