Add decoding to invariant_checker to confirm branches go to their targets

Today our invariant checker does not look for PC discontinuities after a branch b/c it has no decoder.

I have a local branch where I started adding decoder use to the checker for looking at ud2a in our signal test but I hit build issues w/ dup syms on Windows plus complexities with the module file and using raw2trace's mod mapper and I abandoned that branch: still have it locally. Now that we have encodings in the trace itself it will be much simpler (no mod mapper; may still hit link issues).