Fix initialization of th_task_state on each thread on expanding hot teams.

The th_task_state was initialized from the master thread's value, or
from its memo stack, but this causes problems because neither of those
may have the right value at the right time. However, other threads in
the team are guaranteed to have the right values, so we change the
initialize the new threads' th_task_state from the th_task_state of
the last of the older threads in the hot team.

Differential Revision: https://reviews.llvm.org/D142247
Fix #56307.