Cache thread details when populating suspended thread state

[dbwiddis]

Coming from discussion on #2487

In WindowsOSProcess when USE_PROCSTATE_SUSPENDED is true, we fetch all the thread details to populate the process state. However, we never save those for use in the thread details query. This is likely the most efficient way of populating thread counters for all processes and should be saved and used in preference to the performance counter query.