Add fast-forward feature to skip N instructions in drmemtrace analysis tools

This is a feature request to make it easier to simulate a subset of a long trace. Today, this would be done by running a trace splitter offline. The proposal is to support skipping forward N instructions by seeking in the trace file, to make it usable online during simulation.

The records are fixed-size, but the instruction type density is not uniform, so we'd have to do something like embed markers with instruction counts every N records so the seeking can find the proper instruction boundary. We could limit the fast-forward jumps to every N instructions.

There are several features which may not interact well with this feature, where we want to only emit non-changing data once early in the trace and assume a trace reader can cache the data:

• Instruction encodings (#5520 (closed)) only included for the first dynamic instance of a static instruction, to save space. One solution is to re-emit these at the fast-foward point.

• Physical address translation markers (#4014), which are only emitted on the first instance of a new page (or when mappings change, if that can be detected). Again, a solution would be to re-emit these at the fast-forward "checkpoints".