Create a trace format and create a trace and replay framework

XLS JIT'ed code can be integrated into larger simulation frameworks as part of a system-level simulation. If that system-level simulation detects a problem it is useful to be able to replay that failure at a smaller scope (ex at the XLS block level).

This issue is to create a trace format that said system-level simulation can dump, as well as create the infrastructure to take that trace and simulate an XLS block/proc through by itself.