[VM] thread sorting

[Uday S Reddy]

Hello,
How can I sort threads by date, so that the last message (by date) of a
thread will be always at the bottom of the thread and instead of sorting
threads by the root, I would like to sort them by the last message.
some subject
├►
│└► (A)
└►
└► (B)
some other subject
└►
└► (C)
---> C later than B later than A

In VM, we do this by sorting by "activity". That means that the threads
with the most recent activity get moved to the end.

Cheers,
Uday