Also turn on the command trace unconditionally for TestThreadPlanCommands.py as the
tests for the Ubuntu bot don't seem to run with -t making it hard to see why this is
failing remotely.
that were not reported by the OS plugin. To facilitate this, move
adding/updating the ThreadPlans for a Thread to the ThreadPlanStackMap.
Also move dumping thread plans there as well.
Added some tests for "thread plan list" and "thread plan discard" since
I didn't seem to have written any originally.
Differential Revision: https://reviews.llvm.org/D76814