Embed the CQueue in a ProcessId

[NicolasT]

For most operations (e.g., link, monitor etc.) it's likely fine to go through the nodeContextProcesses Map to look up some target process and make modifications. However, when sending a message, going through this Map is quite wasteful. Instead, we could consider keeping a reference to a process' CQueue in its ProcessId, so send pid a doesn't need to go through the process table and can instead simply retrieve the CQueue from the ProcessId and deliver a.