Create wrapper class for Hermes CDPAgent + CDPDebugAPI (#43352)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/43352

## Context

We are migrating to the new Hermes `CDPAgent` and `CDPDebugAPI` APIs in the modern CDP server (previously `HermesCDPHandler`).

## This diff

Adds the `HermesRuntimeAgentDelegateNew` class to provide a swap-in replacement for the existing `HermesRuntimeAgentDelegate` when we enable this via an incoming feature flag.

Changelog: [Internal]

Reviewed By: motiz88

Differential Revision: D53810356

fbshipit-source-id: c63684252230a747ecf0bd8cbb6f4e22052ed9bf