[OpenMP] Add missing `tt_hidden_helper_task_encountered` along with `tt_found_proxy_tasks`

In most cases, hidden helper task behave similar as detached tasks. That means,
for example, if we have to wait for detached tasks, we have to do the same thing
for hidden helper tasks as well. This patch adds the missing condition for hidden
helper task accordingly along with detached task.

Reviewed By: AndreyChurbanov

Differential Revision: https://reviews.llvm.org/D107316