Linux Build Error

Linux build is currently failing. The reason for the failure is because `Network` is not a swift linux package. Network is used in the mock rippled implementation for testing.

https://github.com/Transia-RnD/XRPLSwift/blob/main/Tests/XRPLSwiftUTests/XrplUTests/MockRippled.swift

- [ ] Rewrite the MockRippled to use `SwiftNIO` instead of `Network`