Summary:
This diff introduces a new integration concept (called RuntimeExecutor) which consolidates `Runtime` and the dispatching mechanism.
As simple as that:
`using RuntimeExecutor = std::function<void(std::function<void(facebook::jsi::Runtime &runtime)> &&callback)>;`
Reviewed By: fkgozali
Differential Revision: D12816746
fbshipit-source-id: 9e27ef16b98af861d494fe50c7e50bd0536e6aaf